They’re portable and don’t require that I install anything. If I’m looking for an odd tool, it’s usually the easiest way to download and test something out. It’s just nice to have a standalone executable.

Flatpaks are fine, I really have no problem with them in theory but I spend twice as long configuring them as I do with a native program, and I have to trust that the maintainer is affiliated with the project, which isn’t always the case.