Is "no contract" to be taken super-literally? Do they not ask to sign a terms-and-conditions document at least? or ask for ID at least to ensure you're a resident of the jurisdiction? I always thought "no contract" was just a term of the trade to mean "no post-payment contract". I'm skeptical they're willing to have anonymous users.
> Do they not ask to sign a terms-and-conditions document at least?
Not when I got one (… two … no, three…). No idea what current rules are, may have changed, but back when I lived in the UK you'd find stacks of SIMs on supermarket shelves for £0.99 each, no questions asked. Topping them up was also no questions asked.
It's possible there was a tickbox somewhere for "you agree to the T&Cs", that's the kind of thing that I'd not even remember, but no actual signature was needed.
Germany (where I live now) needs a proof of ID to register a SIM, so did Kenya when I visited, but the UK hadn't done anything like that by the time I left the country.