On Unixy systems, spaces are uncommon because so little software can deal with them, so that people are trained from the very beginning to treat spaces like the plague. I do it too - I've been burned by treatment of spaces in shitty 0.x level software so many times (25+ years ago) that I now have an intuitive aversion of anything with spaces.

Spaces in filenames are a reality though, especially on Windows (where the home directory itself used to have spaces in it, and also where many home directories on corporate networks are on network drives and start with \\), and any software that can't deal with those kinds of paths has just not been exposed to much (if any) real world use. That was the point I was trying to make - software that can't handle anything but the most bog-standard path names in its core configuration is 'hey guys look at what I hacked up yesterday evening' quality at best. (yes yes it is possible to imagine exceptions, like software that is decades old and ported across platforms; I'm talking about something new that is meant to solve a general problem).