Is it though? Do you actually live in the UK? Do you want to know how often it happens in London?

I live in the UK, though not in London. I can count on one hand the number of times a group of children asked me to buy alcohol for them. So it's not that it doesn't happen, but it almost never happens.

Compare standing outside a supermarket, repeatedly begging passers by to commit a crime for you every time you want alcohol, with the one time action of installing a VPN client on your device and it's obvious one law is enforceable while the other is not.