So, What's the Problem With Letting People Bot in Customs Again?
A while back, a long while, Riot removed the XP and IP gained from custom matches against bots. This was because the large majority of players (substantial, huge, there was a graph and it was disgusting) were playing until the 7 minute mark (then the threshold for getting XP and IP) and then disconnecting and restarting.
Makes sense, you are a botter, writing a script, you want to raise an account to 30, this is a victimless crime with the fastest payoff. Seems legit.
Riot has removed that, and thus, removed the 'fastest' payoff for botters, but in exchange they have also devastated the 'victimless' aspect. Now botters go into pre-30 Rift games, TT games, and Dominion games (before it was forcibly removed in part because of all the bots).
Riot you can't fight this botting problem. Bots will always exist, there's no clean answer to the situation. So why not just make the crime victimless again? Let bots power level in customs where no one can suffer through their inane nonsense and lose matches and get tilted. Is the number of free level 30 accounts you remove by cutting down the time that botters spend raising one account really worth the stress and pain of your players?
A further point of issue: One of the reasons botting used to be such a problem was the free RP gifted at level 3, which players could then use to gift stuff to their mains. This has been answered in the form of 1) No gifting until both accounts are level 10, 2) You have to be friends with an account for 2 weeks and 3) No more free RP at level 3, period. So with all those steps taken to make botting less profitable to main accounts, I think there's less of an issue with letting them run rampant in Customs.