Apple Announces Native HEVC Support In MacOS High Sierra and iOS 11 (cnet.com)
New submitter StreamingEagle writes: Apple massively improves the quality of photo and video experiences, including High Dynamic Range. High Efficiency Video Coding (HEVC) can double photo and video storage capacity, and cut the time to upload or share by half. HEVC video compression and HEIF photo compression are coming to iOS 11 and MacOS High Sierra. Sean Hollister adds via CNET: "Having used HEVC quite a bit myself, I can vouch that it takes up less space. I recently transcoded roughly a terabyte of video to HEVC on my Windows PC, and saw hundreds of gigabytes of savings."
Youtube.
If you want one simple reason (there are plenty of other more complex ones) Youtube uses VP9 and you get better quality per bit when you can stream from them in VP9 instead of H.264. Given that Youtube is, by far, the world's largest video site that is good enough to support it right there.