That's where our opinion differs. I don't think HEVC is a bad codec per se & diabolize it.
The tech is fine. The licensing sucks.
HEVC is supported today in HW in many appliances. Today, you don't have youtube HDR in iphones, a big market, and many TV, like LG.
Again, the pragmatic option was to keep supporting the current codec, which has a limited shelf life anyway. HEVC replaced H264 which itself replaced H262 aka MPEG-2.
Contrary to Flash, HEVC obsolescence is planned, it won't be competitive against the next generation video codec & industries have chosen at last to get rid of MPEG & go patentless with AV1
VP9 is an unecessary distraction from Google cutting users from content where they can support both
It's their (Google) service and they don't want to have anything to do with HEVC, which to me is perfectly understandable. And, technically, VP9 was released first. For Google there wasn't ever an AVC to HEVC transition. They went from AVC to VP9.