Generally, its not that I have too many tabs as much as I have some tabs I leave open all the time and want to condense down a bit.
For example, at work I use Chrome for my main web work, and FF for my... uh... shit like this. So I have a bunch of Chrome tabs open that I know I'll have to make changes to again in the future, so they stay open. I also have 'projects' which contain a bunch of pages that are all related to each other. Being able to group those together and collapse makes it easy to quickly get back into them when someone wants a small, insignificant (sorry, extremely important!) change to them that needs to be done yesterday, and I can eventually just throw the group away once the project is mostly complete and not going to be touched by human hands ever again (until a year later, when it suddenly becomes a critical problem for someone, and thus a problem for me... I'm not complaining, you're complaining).
At home, I mainly use Firefox. I have an extension that allows me to have tab groups, but its not as nice looking as the built-in Chrome version (Simple Tab Groups, which is actually quite nice, but not as pretty as the Chrome ones). I have a group for my usual fucking around stuff (Discord, YT, Kbin, DIM (Destiny app), wiki for whatever other game I'm playing), a tab for my streaming stuff (which I don't use often, but as I have a few container tabs for logging in to my brother's account for a handful. I like to just leave those open so I don't have to worry about it), and a group for my "working from home" stuff like email/OneDrive and a smaller amount of pages I always keep open because I'm always editing them for work.
So all in all, I don't have like a hundred tabs open at any given time, and I could make due with just having them all bookmarked and open them as need be... but honestly, that's a bit of a hassle and would also either leave me with a ton of useless bookmarks after a month or two, or require me to curate my bookmarks every month or two. Versus just having a tab group I can just kill off once I know I'm done with their work.