Why indeed. Is that because bookmarks are too clumsy to use, and don't save your scroll position and other user input?

Any time I'm working on something, I inevitably end up with 20-30 tabs with different things I'm referencing. Especially documentation. I think I have around 6-8 open when I'm not doing anything, since I pin some web apps (e.g. Facebook Messenger) or dashboards.

It's also the best way to browse image galleries: middle click everything into new tabs, navigate them with the keyboard, and close them as you go. Beats clunky JavaScript lightboxes.