During my time I spent in the USA (I’m from Australia), I was very surprised at the way money and transactions worked. This was 2014/2015 - in Aus pretty much every consumer bank already had paywave (or whatever compatible technology) cards, which either paywave or also ask you for a PIN if the transaction is large, and here I was in the USA being asked to swipe my card and sign for things.

In small transactions (say, less than $100), no-one really cared - I would scribble my signature on a docket, no-one would double-check it with my card, everyone went on their way. Signatures were required but not respected or checked. In large transactions (I bought a MacBook, for example), the staff could not care less about my card or the signature scrawled on the back, but they would only take my money after I could produce some photo ID (a passport in my case) showing that the name on the card correlated to my face. In this case signatures were technically required but totally ignored because they’re easily forgeable. (A fact I’ve always been bemused by is that the signature is on the card - if you drop your card or something the signature is right there).

End of long story - how valid are “just signatures” legally? As someone with zero legal experience (clearly qualified to comment) I feel like other evidence showing that someone received and signed the document would be much more valid than just “the signature” by itself.