Encoders for vp9 and h265 have a long way to go before they can compete for real-time usage, such as WebRTC.

because they lack hardware implementation?

I think vp8 doesn't have too many hardware implementation either. h264's situation is better though.

It's only the fallback "mandatory-to-implement" codecs they're talking about. If two devices can speak vp9/h265 or others not yet invented, they can use those instead.