Unlike other commenters, I agree with you. Debian based systems are less suitable for desktop use, and imo is one of the reasons newcomers have frequent issues.
When installing common applications, newcomers tend to follow the windows ways of downloading an installer or a standalone executable from the Internet. They often do not stick with the package manager. This can cause breakage, as debian might expect you to have certain version of programs that are different from what the installer from the Internet expects. A rolling release distro is more likely to have versions that Internet installers expect.
To answer your question, I believe debian based distros are popular for desktop because they were already popular for server use before Linux desktop were significant.