Chances are 4k simply isn't going to ever be something available on "all devices"; it's not going to work on shitty phones, it might not work in iOS because of Apple's lack of VP9 support, and ironically laptops / pcs without a GPU might not be able to stream in 4k.
Granted many of those devices aren't hooked up to 4k screens so it shouldn't matter, but I feel like Google is afraid to just tell people that or at least haven't figured out how to properly mitigate it (write into their software some way to detect the stream being handled poorly, etc.)
Granted many of those devices aren't hooked up to 4k screens so it shouldn't matter, but I feel like Google is afraid to just tell people that or at least haven't figured out how to properly mitigate it (write into their software some way to detect the stream being handled poorly, etc.)