Reason that Google isn't seeing more is a) some BigCo v4 holdouts b) happy eyeballs sometimes landing on v4 because their v6 is shitty 6rd or something (e.g Free SAS)
Free has ipv6 enabled on 100% of their customers, and while sometimes their software has a few issues, it's working perfectly fine. People just get pissy because Free refuses to pay for peering with Google for e.g. Youtube, and it feels slower, even more on v6.
The only ISP not putting out v6 widely is SFR, and thankfully they've gone bankrupt and we will be rid of this scourge.
I am on Free (after a few years with Orange because Free could not bother to provide fiber here) but I am considering switching to Bouygues because I pay too much for the connection.
The connection is solid, though - thus my lack of enthusiasm.
Here in Belgium it's the other way around. we've had IPv6 for over 10 years for basically all home internet, but mobile is still ipv4 only. Not sure why since it's all the same companies.
I'd however mention, the two biggest ISPs that remain today both have adopted IPv6 on their fiber connections. They're also heavily using CGNAT for IPv4. It makes sense, the volume at which they're working makes dedicated IPv4 very uneconomical.
Even smaller ISP have done that. But I switched to JioFiber last year and it loses its IPv6 network every week for a few hours. Diagnostics tell me that everything is okay and the customer support just doesn’t understand the problem.