Why Junglers do what they do.
Dat Rina posted one of these to help players understand Supports so I decided to follow his/her example and help people understand the Jungler. Also, as a disclaimer, this is my view on Jungling. Many players do not understand why Junglers do what they do so I am here to explain.
1) Why doesn't the Jungler gank 24/7?
First off, just to make it clear, our job is not to gank 24/7. Our job is to provide pressure around the map, keep an eye on the enemy Jungler, and secure objectives like Baron, Blue and Red, and towers. We are not your babysitters. Some of us want to farm so we can build up Devourer Stacks or invade the enemy Jungle so we can shut down the enemy Jungler. Sometimes, we're at Dragon, and we are securing an objective. Basically, we have more tasks to do than just ganking.
2) Why doesn't the Jungler gank when I am losing my lane?
We do not gank your lane if you have lost your lane because it puts our lives in danger. If the enemy Riven, Renekton, Ahri, Akali, Vayne, or Lucian is 7/0. that means he/she has the potential to outplay a 2v1 or a 3v2 due to the raw power they have. At that point, the reward for ganking that player does not equate to the risk involved with facing that player. Consequentially, we will compensate by feeding another member of our team because if a Jungler can constantly get kills from another lane, that means two players are getting fed off that lane: the Jungler and the respective laner(s). And call us selfish, but Junglers need to get fed just as much as laners do.
Sometimes, we know the enemy jungler is a strong counter-ganker, like Lee Sin, Elise, Nocturne, Warwick, and Udyr. In that case, we will ask you to ward. We are less inclined to gank if there is a chance that the enemy Jungler is waiting in a bush.
Additionally, sometimes, Junglers get smack-talked by their own teammates. When that happens, we do not even want to touch your lane. If you want a gank from your Jungler, ask nicely and do not bash him/her if the Jungler chooses to not come.
3) Why is the Jungler not giving me Blue?
It is our buff, and it is up to us whether we want to give it to you or not. Blue is in our Jungle, not your lane. I get to decide whether to take it or not. Giving Blue is an investment. If we are confident that the Mid Laner can make good use out of the buff, then we might donate it. However, if the Mid Laner is 0/3 and trying to recover, we are not giving it to the Mid Laner because he/she might die and give up the Blue to the enemy team. Also, some Mid Laners simply do not make good use out of Blue. We will almost never give a Blue to Akali, Zed, or Katarina, and we will never give a Blue to Yasuo.
If you are a Mid Laner, and you would like to have Blue Buff, just ask nicely. Nine times out of ten, if you say "May I have Blue?" then we will give it to you. However, if you choose to be mean to us, we may or may not Smite it, depending on who the Jungler is.
4) Why is the Jungler pinging for help?
Sometimes, Junglers get ganked in their own Jungle. When that happens, go help immediately. We usually do the same to you so we'd like you to return the favor. And, objectively, if the team's Jungler dies to the enemy Jungler, that means two things. First, your Jungler is weak and will provide weak ganks. Second, the enemy Jungler will be strong and provide strong ganks for the enemy team. By helping your Jungler out, you help the team since the Jungler will be strong enough to provide good ganks for the team.
Other times, we see an opportunity for an Objective like an early Dragon. Unless it's a Patch 4.20-4.21 Pantheon, a Level 6 Shaco, Warwick, or Nasus, we cannot take Dragon by ourselves. Go help him out. If you do not see this call as a good idea, tell the Jungler to back off the objective, and try to provide a reason such as "We're low, Fizz MIA."
5) Why is my Jungler taking my minions?
This is called minion tax. If we gank your lane successfully, we will take a few minions. This will compensate for the time we spent in your lane. Sure, securing a kill grants 150 or 300 Gold for us, but we also need a bit more experience from the minions. The experience gained from killing an enemy Champion surprisingly is slightly less than the experience we gain from staying in the Jungle.
Also, we usually hit or kill the minions to push the wave faster into the opponent's Turret. It's a basic laning tactic. By pushing our minions into the opponent's Turret, the Turret will take waste the gold and experience that the enemy laner could have had. This lets you, the laner, recall sooner and roam if you would like.
If you have backed, and there is a huge wave incoming, we are taking that wave unless you have Teleport ready. We are not letting that wave die to the tower. As mentioned before, if the Turret kills the minions, that is wasted gold and experience for the team. It is better to let your teammate take the gold and experience than to let the Turret mop it up.
6) Why does my Jungler want Baron or Dragon instead of a Turret?
Turrets are not worth more than Baron or Dragon, mathematically speaking. A Turret just gives gold, some experience, and a bit of map control. Dragon gives a permanent buff, and Baron gives a huge buff for 4 minutes. Both buffs from Baron and Dragon help take turrets easier because of the buffs. If you'd like an in-depth explanation, here is a link to another post I made about a month or two back.
http://boards.na.leagueoflegends.com/en/c/tips-tricks/sN3QBRX5-real-value-of-objectives
7) Why doesn't my Jungler play [enter "OP" Champion here]?
We have a choice to what Junglers to play. We may not have the "OP" Champions so we physically cannot play them. Sometimes, we do not like playing those Champions, like how I hate playing Warwick or Lee Sin. Sometimes, that Champion would not fit the team composition well or would die to the enemy team (i.e Warwick with a magic-based comp or Master Yi vs. a heavy CC team). The same reason why you may not pick Fiora, Akali, Fizz, or Kalista in Patch 4.20 is the same reason why we don't play Warwick, Udyr, or some of the other "OP" Champions.
With that being said, we choose champions that you do not see often. Sometimes, we play for comfort and stick to champions we know. In my case, it would be Nocturne, Jarvan, and Nautilus. I would be better with playing Nocturne instead of Warwick because I am comfortable with Nocturne, and I am confident that I can play him well. That's the same reason why we see Top Laners go with Aatrox, Mid Laners with Viktor, ADC's with Ashe, and Supports with Taric. It's for comfort.
8) Why is my Jungler ganking for a winning lane?
By ganking for a lane that is winning, we help that lane snowball so we can take down the tower earlier. This lets the respective laner roam around and help other laners out. Also, this lets us get fed off the enemies in that lane. If we can get fed substantially from a lane, we not only put the enemy(ies) in that lane further behind but we also put ourselves further ahead. That lets us transfer some of our power into your lane later.
Not to mention, morale is something that is overlooked in the game. By camping an already-behind opponent, he or she will be more and more demoralized to play the game well, and this can turn that player toxic. Let's say we have a stereotypical Riven player (no offense to Riven mains out there). If we know that she will rage when behind, the Jungler will repeatedly kill her over and over to get her to rage. That will demoralize not only that player, but that player's teammates will be annoyed at the rage.