It's a FOMO hoarding thing or ADHD thing. People place great value on their passing interests. They see something like "oh that would be good to read/watch" and the tab structure becomes a kind of combined to-do and reminder list. Closing the tab feels like giving up, forgetting, or losing an opportunity. If the tab is still there, there's still an opportunity. Bookmarks don't work because it's out of sight/out of mind.

This isn't an argument for keeping so many tabs. It's an explanation. People will still feel the weight of so many things on their list and they really should just let them go. They'll feel lighter and they won't miss it (except for when they do) 👀