I guess the reason I chose Qt over any web-based frameworks is I wanted a standalone app that would launch in a fraction of a second and just do its job. I don't think a webapp (if that's what they're called) would give me that. At the time, it seemed that Qt would work well and, as a bonus, be cross-platform. I had some Python experience to boot which helped.
Edit: I do have a personal site at https://www.fellerts.no/ but it's entirely static, no real js to speak of.