Bookmarks are too permanent. Tabs are for things I'm interested in but don't really care about (and so I'll probably never get back to). I use different windows for different types of things, so it's organized. I just have an alias to kill Firefox when I want to game.
yeah IDK how the fuck tabs overtook bookmarks as the way to save websites. i got into the bookmarking before tabs were even a thing. seeing people with 6 year old tabs amongst the thousands makes me dizzy. there's so so much better of a way...