Why ban players if they are just going to make alternate accounts?

I know permanent bans are supposed to remove the toxic players from the game, but in reality almost all toxic players will just go and make another account to circumvent the ban. So the only "real" punishment for a ban is losing the progress they made on their main account? I know Riot's tests with player reform through secondary accounts had around a 5% success rate, but I can imagine it being even lower without the system. What's the point in reforming if you're not going to get anything back? Toxic players will just grow to be averse to spending money on the game and learn not to get attached to their accounts. At the same time, what can Riot do about this? An ID ban is only really effective if the player is well known enough within the community to be able to be identified, and an IP ban is easily circumvented through VPNs and IP changes. Therefore, it would seem that Riot's only motivation for banning players would be to force them to spend RP on things that they had already purchased, which seems highly unlikely and practically like a conspiracy theory. What are your thoughts on the matter, and what could Riot do to a) reform toxic players who will continue to play the game, or b) prevent toxic players from continuing to bring down the community at all levels of play?