Mainly because maintaining it consumes resources. I appreciate you’ve wanted it properly supported for some time, and it will still be possible for someone else to maintain their own versions of the libraries in the future.
However, converting apps to Bluez or kf5bluezqt would be better in my view.
To add to the general discussion, the best reference docs for Bluez 5 in my experience are those in the bluez source tree. They’re terse, and lack useful examples, but all of the info is there. I agree that @piggz’s qble repo linked is a really great resource too (I’ve referred to it many times in the past).
@martonmiklos: your BLE Scanner app covers a lot of functionality, so I had a go at switching it from QtConnectivity to Bluez. Maybe it’s useful for others who are looking at making the switch. I included references to the docs and equivalent dbus-send calls to help add context to the code.