In spite of your conntrarian phrasing you've kind of only sold me on tabs being a more advanced hypermedia bookmark than the simple bookmarks we've been given.

> they keep sessions (a)live (audio/video, chat, where you stop reading)

I'd also note that at 7500 tabs your computer almost certainly is not keeping those sessions alive. It's stunning how far we can get but wow, watching Chrome over the years claw it's way towards being fast to load & staying responsive, in spite of being many 100's of tabs in on a mid-range 201X phone was an incredible saga of improving software architecture. It got better and better.

There's whole means of backgrounding & persisting pages (and of preloading new pages) that's just amazing.