I think as the number of branches grows, people will just start to drown in the huge list of unmerged branches and will start to work as if only trunk/master exists.

With a text file that summarizes all the project's main line of history in a structured, linear way, it's very simple to extract just what you're interested in or find all the entries for a particular thread of research across history, quickly.

I don't think the tooling around git branches really enables that kind of operation in a quick, easy way, partly due to the inherent nature of branches.

I'd be interested to see what your hypothetical workflow turns out like in practice, though. It's certainly possible I'm just not seeing the potential.