The short answer is, Meta.
I've thought about this same concept in my first days of LoL: Why not play jungle caitlyn or rek'sai support? And the reason is that some champions are IMMENSELY better in certain roles, like jungle warwick. Some roles even weaken certain champions.
Lets say for example you took warwick in bottom lane. As a melee champion with a lack of poke, you will EASILY be damaged down by ranged marksman and heavy crowd control supports that occupy this role. You will fall behind very quickly and eventually start dying because you have been starved of gold and experience, leaving you under-leveled and very squishy. With no gold, you won't be able to buy damaging items, so not only are you an easy kill that makes the enemy stronger, but you also have little to no impact on the game at all in return.
You've given the enemy team an insane boost and made the match-up unfair, and obligated your team to sit through a 20-45 minute beatdown, in a game that is extremely competitive. You've set off a dire, infamous fuse that is "feeding."
Now, in regards to warwick
specifically, as a jungler, you can make the most of your W. As a jungler, early vision of you is not nearly as common as you in lane, so you can use your W to find free targets to get the element of surprise on, and help other laners stay stronger than the opponent. If you try roaming while playing a lane, even half-good players will have the map awareness to see that you are missing, and will hover around tower until you have been seen again, or ward up. This element of suprise is one of the things that makes warwick so scary to fight.
Try to remember your allies' perspective in this team game. If you play poorly or unconventionally, this WILL set people off. The better/conventional player you are, the more people will like you here.