Jax used to be played Botlane
http://forums.na.leagueoflegends.com/board/showthread.php?t=1122460&page=1 http://forums.euw.leagueoflegends.com/board/showthread.php?t=364460&page=2
after this, Jax botlane became a pick in soloq for 4 or 5 months before massive nerfs
the reason people never played anything but adc was because melee sucked in this game and riot never was able to do viable melee carries except jax, yi and trynd sucked above diamond
Now we have yasuo and fiora, why aren't they played bot? why isn't jax played bot anymore? because we buffed adc after 2012, this is the only answer i can find we buffed them in 2013 with xypherous, and then in 2015 with the rework
B. Horribly overpowered numbers and an unfair advantage. 
worth the gold you spend on it. Something like that. Because otherwise, melee champs have to work too hard just to survive, let alone thrive, against ranged champions in lane.