maybe because he sees things different and either thinks your lane isnt gankable efficiently, other things are more important etc. always remember that your jungler is not trying to gank more often than the enemy jungler but overall pressure him.
he lanes in the jungle. if he goes to counterjungle the enemy, its then UP TO YOU to not die to the enemy jungler because you should KNOW that when there are no camps for him to take, he has to gank gank gank or he loses the game. same thing with toplane, what if toplane destroys enemy hard early on and gets a kill level 6 and then freezes, denying the enemy toplaner completely every single cs and most experience?
ofcourse the enemy riven is gonna roam and try to flash on mid or botlaners. its not toplaners job to prevent that, he is allready doing his job perfectly fine. its now YOUR job to not die to that riven and let him win you the game.
you know how easy it is to lose lane and how quickly you can fall behind. same in jungle. he ganks once or twice unsuccessfully and boom, instantly fucked himself. then what? im level 5, enemy laner is level 6 on the way to 7. then he ganks with ults and flashes and what do you want me to do? should i go and farm level 6 right now so i can do the same or should i keep ganking like crazy and pray to god that some of them will be successfull? lets say i decide to farm because my lvl 6 ganks are really just much better, and he ganks midlane successfully and even takes midlanes flash. now what? he got gold, he got exp, he got a kill. he doesnt need to go farm jungle much, he just wastes his overflowing smite on a quick camp and comes again because he knows you are bad and you have no flash. instantly killed again. sure, you didnt learn anything from this in midlane, you just kept laning like a dog thats fetching a stick and got ganked again, maybe 5 times in a row. why not? you are free money. its up to you to fix that, not up to your jungler.
now your jungler finally got level 6 while you are allready 0/3 due to your own sucking and you are allready blaming him so the chance of him feeling like its a good idea to gank you is slim to non existant. so hes like "hm who do i gank, my botlane is caitlyn janna vs lucian thresh and our team is constantly pushing them into their tower, so probably not them. my toplane is vladimir vs hecarim, so damn, fuck, probably not him either. and im damn sure not to gank this retarded ahri who allready fed zed 0/3 midlane. so what am i gonna do? probably just farm until an opportunity arises and counterjungle/ward for my team."
and man, ganking really depends on laners too. what can he do if his laners trade so badly they couldnt follow up a gank anymore or just blow their cooldowns or cant handle their wavecontrol. if he ganks a retard laner and gets counterganked, instant doublekill. so he maybe wants to secure jungle vision and jungler tracking first or just doesnt gank retard lanes at all. like if i go to a syndra lane vs leblanc and i know my only chance to ever gank this lane is if syndra accepts a bad trade RIGHT NOW to make leblanc waste her W and then stun her right afterwards, but first syndra doesnt get the point that SHE HAS TO MAKE A MOVE and then wastes/misses her stun, i will simply never go to that lane ever again. deal done.
same if im going to invade top jungle around lvl 4-5, warding it, getting jungle tracking through him being not here so hes either recalled or around bot side and i TELL my botlaners that or at least ping them red/yellow and they INITIATE A FIGHT THEMSELVES! and get ganked, i will NEVER gank them ever because its 100% obvious that they are bad and a gank would be impossible to succeed, except by pure coincidence. i rather gank this darius 5 times who makes sure to never let riven become a factor ever and then helps me control the jungle. and yes, if all lanes are bad, i rather just farm and only gank with my big cooldowns or save them for objectives for when I feel its a good call.
and if the jungler thinks its worth farming 20 minutes only and then going and being usefull, then its his decision and you have to accept it. same as with midlaners who feel like they just want to farm and hold their tower/pressure enemy tower but not roam botlane or same with toplaners who simply need to use their TP in lane all the time to not fall behind so they cant TP bot. its not up to other people to win or help your lane, they are trying to do their job and if you fuck them up over it because "omg you could do so much better", yeah, sure, they probably could all do better and so could you.
im not being toxic here, im just revealing a part of the truth to you that was hidden until now. you can either accept it or keep bitching.