If they don't know they're being quarantined, there's no reason for them to find a way around their block. They'll eventually tucker themselves out and move on to whatever their internet equivalent of burning ants with a magnifying glass is.

I used to run a small MMORPG. I only had to ban a player once but when I did they made it their life's mission to get around it and spam profanities. They went through every proxy in existence and I had to resort to banning whole IP ranges to keep them out.

The same reason people get shadowbanned. If they know they are banned they will attempt to work around it.