AV1 is not new anymore and I think most of the modern devices are supporting them natively. Some devices like Apple even have a dedicated AV1 HW-accelerator. Netflix has pushing AV1 for a while now so I thought that the adoption rate should be like 50%, but it seems like AV1 requires better hardware and newer software which a lot of people don't have.

Dont forget that people also view Netflix on TV’s, and a large number of physical TV’s were made before AV1 was specced. So 30% overall may also mean 70% on modern devices.