Maturity and the breadth of the surrounding ecosystem, for one. Flutter is looking very promising long-term, but it's going to take some time to evolve past a mobile app framework.

Qt is most widely known for the UI framework, but it actually has far more functionality under the hood. Qt's core target audience values those features. Most of the people who see Qt as a simple UI framework don't.

Like the parent comment said, most of the people who are complaining about the licensing costs are on the wrong side of the Qt value proposition. They should use simpler, freely available tools like Flutter or Electron.

I said __embedded__