And it is absurd to call KDE a "tech demo for Qt". 90% of the stuff you can with the KDE you cannot do with Qt because KDE adds a ton of additional functionality. That is why it is so rare to see Qt-only Linux apps, KDE adds so much additional functionality there is pretty much no point.
"Hey, this is KDE. Look at what you can do with Qt"
"Cool, so I just download Qt and I can make my application do all that?"
"Well...no..you need to download tens of megabytes of additional KDE libraries to do most of those things...but the low-level stuff runs on Qt!"
"So why exactly should I use Qt instead of KDE?"
Yeah, great tech demo there...