I've tried all of the commercial phone -> webcam solutions I found that the camera isn't as good as the native software, because the vendor uses some software magic to improve the image quality. The image tends to be very grainy, especially with poor lighting.
Is there a technical reason that none of this software can present a UVC camera to the computer directly?
Where do you see low quality, on the local monitor, or remotely? It's true that the processing and compression means the remote site gets a low quality picture regardless of a good input. But a good input is a good starting point, and if you have good bandwidth, and low latecy (no wifi) then you can get a good quality video stream.
Is there a technical reason that none of this software can present a UVC camera to the computer directly?