I think the passkey standard included attestation for good reasons, but it is obviously also possibly a trap in the sense that I'm sure there were some people on the standards committee(s) envisioning a glorious world where they can flip this on for everyone and instantly all the bad stuff stops.

I have to admit I don't worry too much about the entire internet flicking attestation=true anytime though, because the resulting support nightmare would be ferociously expensive. I wouldn't be surprised that, on its own, it would be more expensive than the cases that the companies flipping the switch are trying to avoid. Which means it isn't going to happen.

The simple truth is metaphorical-Grandma can't handle the degree of responsibility put on the user that strict hardware attestation implies. Netflix et al are more likely to want metaphorical-Grandma's money more than an incremental improvement in their ability to be sure it's an attested login, and won't want metaphorical-Grandma to call Netflix every other week trying to figure out how to log in again. There is no way around the fact that strict attestation implies more user responsibility to make sure they don't lose their token, and at scale, they absolutely will. Work environments can get away with this because work environments have a scalable mechanism to re-verify identity to the extent the business cares about it personally, and reissue tokens. At scale the big companies do not have this for individuals. You can't use hardware attestation without this infrastructure for reverification, and any infrastructure for reverification a large corporation tries to create will have exploitable holes in it.