Given that most UK ISPs (be it broadband provider, mobile phone SIM provider) by default set people up as no pr0n (using their own filters) and customers must give age proof of some sort to opt in to adult content as this makes it lots easier for families with young kids (though obviously filters far from perfect)*
So could be useful if ISP could just pass through a "this person is age verified" token (and even better, this would be anonymized so no tracking across sites).
For many UK ISP users who wnat pr0n, a solution of this type would avoid them giving sensitive data to yet another third party when they have already given it to their ISP
* Discovered the default blocking when denied access to a web page that had info on urinogenital medical issues and was erroneously triggering ISP (pathetic) filter technology (I assume a bit slapdash on matching a few "keywords" with no account taken of overall page content context). So now got a perv flag with ISP so I can look at some medical web sites!