People who use Debian for desktop, why?

These (Mint, Zorin, etc) and Debian are basically the same. You can use either of them and have mostly the same experience once you finish setting up your system. Exception here goes for Ubuntu that forces Snap. I personally go with a minimal installation of Debian and add what I need along the way. If you don't want to set things up thoroughly, you should use a distro you think has the most functionality out of the box.