I may be off the mark but my immediate gut reaction to this question is that distribution/discovery is partly why. On desktop, web apps are more easily distribu

I may be off the mark but my immediate gut reaction to this question is that distribution/discovery is partly why. On desktop, web apps are more easily distributed, especially back in the Windows era. Downloading and installing a windows program was a lot of effort to casual users. But you send someone a link, or they click around the web, and they're in the web app immediately. On mobile, the app/play store makes distribution and discovery arguably even easier. Similarly after that, the macOS app store appears to drive a resurgence in desktop apps (for the Mac at least).