The problem is anything less is essentially a free pass to cheats. If the worst that can happen is a warning of first offence then what’s the disincentive? Cheat as much as you like, you will be warned and so able to stop before you are banned.
So perma-bans are clear messages to cheats. If you are caught you can be banned, suddenly and permanently. There is no excuse for not knowing this, it’s in the TOS and there are many warnings elsewhere, on forums such as this and in game.