people just think its easier to just have tabs sitting around rather than use bookmark

Mentally, I find that leaving a tab open says "I'll get to that soon", where a bookmark says "maybe I'll need that someday". "Soon" might still be two weeks from now, but "someday" might as well be never.

Bookmarks just aren't as visible. Think of it like having things that you need to do laid out on a countertop vs having them in a drawer. If you walk by the counter and have a minute to spare, you can see what you might be able to accomplish in that time and check something off. It feels like you need a lot more free time to even want to open the drawer.

Also, managing bookmarks just looks daunting, and the more you have, the worse it gets. When I'm done with a tab, I just close it.

Sometimes, I'll use the bookmark toolbar, but I don't see how that's better than tabs, visually. It just has better persistence.

Lastly, leaving a tab open can also be used like a post-it note to remind me to do something by a certain date. Every time I see it, it acts as a little reminder so that the thing doesn't fall off my radar. That one gets a little tricky if you have so many tabs open that you have to scroll. I try not to let it get that bad, though.