There are different kinds of DRM. Streaming websites allow different quality for different kinds of DRM. E.g. they allow best quality only for best protected DRM (which should use encryption all the way from Netflix webserver to your display). There's software DRM (decrypting stream inside proprietary blob) which is considered weaker, so you'll receive acceptable quality in Chrome. I don't know why Chrome did not implement the most secure DRM. Hopefully Microsoft will contribute their patches back.