Sound and power consumption. At least in my case those are important if I was going to store data at my mothers house. Power consumption might not matter that much, but HDD sound definetly does. And even with spinning rust hardware cost would be somewhere around 250€ compared to ~20€/month of cloud storage.
YMMV, in my scenario it’s just easier to use a cloud provider.





Age verification is one thing, but I routinely verify my id online. Banking, insurance, taxes, various other government things, car registrations, some of the kids school stuff and so on. We have pretty decent infrastructure in place here in Finland and the entities I identify myself online already has my info anyways. I can use either my banking app or mobile verification to securely prove I am who I claim to be and the systems have roughly the same user experience than MFA tokens.
Each of those are roughly zero-knowledge, the website I log in receives just “User with login token xxx is IsoKiero with SSN 123456789” and the tokens expire after a while. Also there’s restrictions in place that my insurance company can’t just sell my data to whomever unless I opt-in for their “marketing” program (not going to happen) and even then there’s some limitations on how they can use the data.
The same system could be adopted to age verification, but that’s a whole another can of worms.