Perhaps it's a sign that the bookmark UX isn't good (or prevalent) enough.
I generally have four pinned tabs open for email, Slack and Trello, plus another five related to what I'm working on.
It's just that:
1) What goes to bookmarks rarely goes out.
2) usually I and many other people have a few dozens at least of 'related to what I'm working on'. Like a few documentation pages for this, a few documentation pages for that, ten SO pages, ten blog articles on the same topic linked from SO etc. Plus some tabs unrelated to work, but the ones you absolutetly want to visit later and finish reading or something and don't have the time to put them into something like Things or Bear.
Tabs make lots of sense, windows let me organise them into groups of things I'm currently working on. That's all sensible. Anything I come across that I think might be useful to my future self, I bookmark it. Again, working with the provided functionality. Sensible.
When people have 200 tabs open and can't remember what's where, that's what puzzles me. I've seen people flick through dozens of tabs looking for a piece of documentation they saw yesterday afternoon.
We already have the tools that make browsing and researching efficient. People just need to learn to use them.
The problem with bookmarks for most of us is that users don’t typically manage their bookmarks and delete the links they don’t need.
Bookmarks can definitely work, but yeah, a flat list can't. I think a better approach would be something like a mind-map.
Rhetorical question of course. With an open tab I have that information and can go back and forth up the path. Its very useful context to have when I revisit the tab. In my line of work I research many things every day. Firefox open tabs have been a godsend. I literally have 900 to 1200 open at any given time
Photoshop has work flow like this - you can split the undo history into a tree like structure (to a degree, it's not infinite).
Adding and deleting bookmarks at this frequency would be a massive hassle.