I use tab groups for work projects. I am a project manager. I usually have somewhere around 200 long term tabs open at a time with several other transient tabs.

I typically am working on 4-5 projects at a time with some other non-project work categories like status reporting. A lot of my work involves reading and editing multiple web pages or writing updates on web pages based on communications in other channels. I reuse the same web pages multiple times a day and it is not feasible to close and reopen them constantly. Tab groups let me switch between the web pages for projects, read or update the pages, and then switch to another project. If nothing else, it means that I can actually see the titles of most tabs within a project rather than having them all collapse into identical icons. Tab groups helps keep this sane.

I am currently using Firefox-based Zen because its Tab Workspaces gives me the project separation I need. Chrome's tab groups don't offer enough separate between groups for me. I'll have to checkout this Firefox implementation but from what I saw earlier they may be adopting Chrome's minimal separation method of grouping so that may not work. I was using Arc for a while as they have a similar grouping to what Zen does.