I lose all tabs occasionally. Browsers aren't perfect, it does happen after a weird crash, or something. It's exceedingly rare, like maybe twice a year.
With that said, I've always considered tabs to be volatile state. Browsers make their best effort to e.g. restore the previous session after a crash, but if you want non-volatile browser state, you should use bookmarks.
Except I specifically use an extension to ensure tab state isn't volatile (Tab Session Manager, backed up with export tabs urls & a custom script), since I don't want to bookmark 35 pages for a current project, I just want to save them to a named session and have everything avaliable when I return to the project.
I agree that tabs are volatile, although I really wish they weren't. I'm having flashbacks to the quantum switch and having to change most of my extensions. I'd consider switching, but I really don't care for the chromium monoculture that's developing.
Eh, for me only that often if you include stuff caused by a dumb user (aka me). And even then I always got them back one way or another. Usually from %APPDATA%\Mozilla\Firefox\Profiles\[profile]\sessionstore-backups (thankfully there's usually a recent copy, since I'm on a test version) or last resort from backups.
It's not just tabs, but for many users the containers themselves are gone - as well as their cookies and other associated assumed-to-be-non-ephemeral state.
With that said, I've always considered tabs to be volatile state. Browsers make their best effort to e.g. restore the previous session after a crash, but if you want non-volatile browser state, you should use bookmarks.