The final barrier is crappy consumer routers with terrible default settings. Not much we can do but wait for these devices to die because the average user won't buy a new one until that happens
Is that distorted by cellular providers?
I know my wired ISP does not provide IPv6, even when I explicitly asked for it. They do CGNAT for most customers and assign a static IPv4 to anyone who complains (and then try to start charging for it a year later).
The ISP at my previous home was also IPv4 only (although, thankfully, no CGNAT).
When I was using Spectrum, was pleased to find they had (barely-passable) support, SLAAC wasn't a thing IIRC. Google Fiber has done well and so did AT&T's offering
There is a very strong pattern of variability[1] associated with day-of-week. Namely, there is a 5.1% increase of IPv6 traffic on weekends.
This pattern isn't reflected in Cloudflare's version of this chart[2]. Naturally, a curious mind asks, "Why would this be so?"
1. Seasonality - https://en.wikipedia.org/wiki/Seasonality