[Sylos]

Correlation != causation.

And even if that was the reason, your response didn't make anyone any smarter. How is it bad? Which you can't answer, because your only line of reasoning is that it has to be bad, because it's not as popular.

[coldtea]

The UI is bad imitations of native widgets and has been forever. Always in the uncanny valley, except if you're running only KDE.

The setup of IDE/building/ etc is harder than it should be.

PyQT has mostly been the unloved stepchild, with third rate support.

Compile times with C++ are awful.

Major breaks between versions (QT4 vs 5 etc).