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.