Comment by Orphis

HEVC is far from being the most popular codec on the planet in the context of video conferencing. Most implementations are using WebRTC and as it is unevenly supported and AV1 support is becoming more prominent and stable, most implementations are going from H264/VP8 -> VP9 -> AV1 and skip HEVC entirely.

Each new codec to support is adding a lot of complexity to the stack (negotiation issues, SFU implementation, quality tuning, dealing with non conformant implementations...), so it's never quite as easy as toggling a switch to enable them.