In some version of the myth they actually put an exit back to the living world up there. Sisyphus in life tried to cheat death (even succeeded for a bit) which is part of why he wound up in Tartarus. He could stop pushing the rock any time he wanted, but it would mean giving up on escape.
This is a pretty good detail. Makes the story a lot more interesting, and deep.
It feels torturous though. Like he’s just being greedy now instead of being tortured.
Meant to say less torturous.