Common is an exaggeration. You mentioned a handful of examples, most of which are either programmer&#x2F;geek intended or niche (the LightScribe control panel? German&#x27;s official tax app? language course CD apps? Virtualbox? scientific citation managers, etc?)...<p>The fact is a user can go for years without ever using one. And in the tens of millions of apps available for Windows, QT based ones make for less than 1&#x2F;1000...