As far as I can tell, it is an US thing. I can't speak for other countries in the Americas, but when I was in Europe briefly a few years ago, what few purchases I made with a card were all done chip & pin.
In the US, that signature is a on a line right next to the words "I agree to be bound by the cardholder agreement", or some similar language. If I had to guess, the signature was originally supposed to be a mini-contract that yes, you're going to pay back the card company for what they just paid on your behalf. I don't know if such has ever been been taken to court to be enforced, however.
Waiters will chase after you if you forget to sign your check, because they must provide a signed receipt to their merchant account provider if you initiate a chargeback, if they want any chance of fighting it. I'm not sure why they just don't scribble a random signature in for me, because that's all I do when I sign it.
Probably because that's called forgery, and if they were caught doing it it would be a much bigger deal than not getting their money from that transaction.
If the intent is to fight chargebacks, then a false signature seems even worse. A signature that isn't remotely similar to the cardholder's seems less likely to be successful than a blank signature, and presenting such a document may well be fraud.
In the US, that signature is a on a line right next to the words "I agree to be bound by the cardholder agreement", or some similar language. If I had to guess, the signature was originally supposed to be a mini-contract that yes, you're going to pay back the card company for what they just paid on your behalf. I don't know if such has ever been been taken to court to be enforced, however.