I work in software engineering, where we often take screen recordings. The macOS screen recording software by default records to HEVC, so it would be much appreciated to have HEVC support since many of our developers use Mac, as the alternative is Windows.
For me HEVC support is important for Immich, where I transcode all my videos to save on bandwith.
All my extended family uses firefox so I currently use AV1, but HEVC would leverage hardware acceleration as well as work on more devices (looking at you iPhone users).