1) They are instantly town sided. If a town replaces out, you instantly get a fresh perspective on the game. If either alignment replaces out, you now have twice as many opportunities to sort that slot's alignment.
2) They... ruin games. Don't really know how to sugar coat it. As scum, your job is to manipulate the players in the game, not every conceivable player.
3) The fresh perspective on the game point is pretty major. I don't think people understand how big of a difference this really makes, joining a game late without being worn out or having been manipulated.
On top of all of this, replacing out is just anti-competitive. Scum slots replace out way above rand because people generally don't like scum. Aside from this, if you sign up for a game, that should be because you intend to play it. If you are replacing out due to toxicity, sucks, part of the game - and maybe a different site culture issue to target. The only times you should be replacing out of a game is due to a real-life emergency, or, for your mental health. And in the latter case, if you are replacing out for that reason you should not be joining any more games for a substantial time period. The prod deadlines on this site are 48h+ (the day length on most sites) and you are allowed to declare V/LA.
Suggestion #1: shift the community outlook on replacing out to very very bad. Site culture switch. Do not let people join games that regularly replace from games. This does not require a punishment system.
Suggestion #2: track replace outs, and punish people who do it for non-documented reasons multiple times. A temporary ban on joining new games for a time period is good. If you want to allow redemption, let replacing