Why Google Earth has developed in Qt, beacuse of which quality of Qt?

Google earth is GIS software, ans some other GIS software has developed in Qt. My question is..if I am going to develop a GIS software, why should I use Qt for that?

I don't quite understand the question.
You evaluate Qt based on your needs, you either find it fits those needs or it doesn't.

It really doesn't matter whether it fit someone else's needs, does it?

Cheers,
_