I'm around middle age and keep tons of tabs open simply because I have a number of projects/tasks or soon-to-be projects/tasks going at any given point and managing associated websites is easier with tabs than it is with bookmarks. In other words, bookmark management UI/UX is inadequate and tab hoarding is the band-aid.

There's also a higher chance that things will slip through the cracks and be forgotten if I bookmark them, whereas with tabs they're staring me in the face any time I'm using my computer.

tab groups, a very recent feature, help a lot at keeping tabs organized. you can even archive whole groups if you no longer need them but don't want to throw them away