HW support for av1 is still behind h265. There's a lot of 5-10 year old hw that can play h265 but not av1. Second, there is also a split bw Dovi and HDR(+). Is av1 + Dovi a thing? Blu rays are obviously h265. Overall, h265 is the common denominator for all UHD content.

> Blu rays are obviously h265

Most new UHD, yes, but otherwise BRD primarily use h264/avc