Because its a 2v2 lane, its underleveled, and usually if one dies so does the other. Either trying to save, or trying to commit. Not to mention, Drakes. I mean a Fizz/Assassin/Syndra/whatever will have ult while botlane is still level 4. Junglers gank it, becuase its also the lane with the most help. And contrary to popular belief, you cant ward everything early game. And once you fall behind, you are a lane that generally scales off gold. So while your ADC barely lost that 2v2 all in, the enemy ADC comes back with a B.F. Sword and yours might have a cull, or some long swords, or if your lucky, a Pick Axe. So already you are basically unable to win trades without help, and the gold and drakes keep stacking.
The only good thing is its at least a lane you can reliably turn around if you actually go down there and kill it. A fed ADC is still incredibly squishy, and easily killable if you go gank it. Compared to say some top lane morde or vlad 2-4 levels above the jungler and completely unapproachable. So instead of raging about them, how about going down there and turning it around. It is so snowbally, that you could kill the enemy botlane nad possibly get a turret or a mass amount of plates no matter how fed they are; but your botlane will never be able to do it alone.