Its just them being cheap. They probably set every one to a max of 720p, hope most people do not realise (cutting down bandwidth costs) and let them set max quality themselves.
On Roku (actual box not integrated) Peacock has been good quality. Definitely hits 1080P with a decent bitrate. I suspect the software teams only have the bandwidth to focus on a few of the more popular devices (so probably Roku and Apple TV boxes) and others suffer
