Or just clone the same repo multiple times, or have some releases unpacked outside of version control.
Can you run two or more versions and compare their behaviour simultaneously, even debug them side-by-side? I'm sure there's some sort of plugin and IDE ecosystem that you can spend tons of time learning how to configure just to be able to do that, but if all I need to do is to copy the files and rename them, why not?
Do some people really love excess complexity so much?
I would say that this is a bit of an exception though. Most projects are spread across many files and dependencies, so it would be a huge mess trying to manually version those by renaming files all the time. I also rarely want to compare several different versions of my code side by side, so I prefer having all of the old stuff 'hidden away' in git by default.