probably a patent issue... I love x265 for the video file size and a decent video quality
Since then (when they decided that Blu-Ray drives weren't going to be standard in PC) there has been a decoupling. HEVC is a consumer electronics standard, the PC industry is going towards VP9, AV1 and other royalty free codecs.
Up until HEVC most codecs had one patent pool you could pay a royalty to and be good. HEVC had the problems that two entities claim to control essential patents
To this day, the only official way to play 4K Blu Ray on a PC is to get a 10th gen Intel and play back using Integrated Graphics using one of the internal drives made by a drive manufacturer who was utterly shafted by this nonsense.
(It's got to hurt more though that 4K Blu Ray's new and improved DRM was, despite all this, broken less than a year after release. If you are a drive maker, knowing your drives are useless on modern PCs because of broken DRM that Blu Ray developers still insist is necessary must be the most infuriating thing ever.)