From my viewing of Youtube, Google transcodes uploaded videos (typically H.264 stuff) to VP9 only when a certain view threshold is reached, which makes sense from their perspective.
However, I have also noticed that due to the chain of encodes source -> H.264 -> VP9 (latter two available to Google), the VP9 stream is often of noticeably lower quality. Thus, whenever I can, I use an H.264 stream.
This problem will not go away with AV1. In fact, from an archival/local usage standpoint, as others have noted here, AV1 is pretty much impractical due to heavy encoding time increases that will unlikely go away with SIMD as compared to x265 or x264.
As such, from an end user experience point of view, what does AV1 offer that H.265/H.264 do not already?