Some hardware comes with the codec pre-purchased (my laptop does). I don't think I've ever heard of anyone buying a codec in the MS Store, though.
I think most Android phones come with HEVC support. Mine did, anyway; I suppose it's up to the vendor to choose if they want to support it. Apps like VLC will also play the codec just fine. My camera app even records in h.265. This is a phone from Xiaomi, which not exactly known for their great software packages and compatibility.
I'm pretty sure Safari already supports h.265 because Apple switched to HEIF pictures while the rest of the world still just uses JPEGs for everything, and HEIF is pretty close to a single h.265 frame packaged as a picture. Not even Apple would be so foolish to switch default formats on their mobile devices and not support it across their software products.
Browsers don't feel like paying license fees over downloads of their free products and I can't blame them. Mozilla's h.264 decoder is only published along with it because Cisco had reached the license fee cap (which doesn't exist for h.265) and they decided to use their license so that Firefox can play videos freely.
I think Apple and physical disks formats are the only players heavily invested in h.265 right now. AV1 hardware decoding support is slowly coming along, so soon enough everyone can just use AV1 and be free of the proprietary patent bullcrap.