A lot of it has to do with how laptop web cams work in general and it is not only Apple's problem [1].
A way to improve this situation a bit would be to be able to use the camera of an iPhone as a web cam, either over USB or wifi. You still have the compression and USB transfer, but at least you use the better optics of the phone. There are third party tools, such as EpocCam, that can do it, but require the installation of drivers. This should be a first party solution, in the same fashion as the "take photo" option from the right click menu on Mac OS, which uses an iPhone to take a photo and paste it directly on the open application of the computer.