Well a BOT it's not an HACK, it's a BOT, that's why when we read ToS of the games they say.
You should not use 3rd Party Software like hacks, bots, etc.
So don't call the samething to two different things, example CD hack, was an hack.
Bot it's just a script, that will automated something, it will do the same thing over and over 24h per day while running.
That's why I call to NHC BOT, AFK BOT because allows you to be away from keyboard but still playing games :).
And the only function of the NHC BOT, it's to play games. And playing games (in this case only costum games and coop vs ai) you gain EXP and IP.
Initially was to abuse the Referall system since you got rewards for having lvl 5 or lvl 10 accounts. However since RIOT bans people that abuse this system with already 3 banwaves.
Now I use more to do Power level from 1-30 :), you can still do refs, but at your own risk :p
And regarding bans, you don't get ban for using a BOT that plays games, you get ban for many reasons, usually hacks or abuse of exploits that gives you advantage ingame are a reason of BAN.