As of this month (April 2018), the big four card networks have stopped requiring (USA) merchants to collect signatures if chip is used. They had already waived this documentation step for the ~80% of transactions below $50.

With the wireless payment cards, it's even more efficient then cash. Just put your card up to the machine and it takes the payment. No pin or anything. Limited to under a certain amount though. And it does sometimes ask for your pin now and then to make sure it's you.

I only sign paper at restaurants. If a signature is needed at a retail store, I usually sign a digital pad.

Increasingly you sign (or in my case scrawl a wiggly line) a pad but I still sign paper fairly regularly. One of the issues with PIN in the US is likely that you'd have needed a whole new workflow and mobile devices at sit-down restaurants. It would arguably be a better system to move to settling up at the table, but it would still be a big and expensive change.

You needed new devices anyway to switch to chip, but I think it is a cultural issue with tipping. Some people really like that the server doesn't know how much you tipped until you leave.

Yeah, that may be part of it. It's not really rational but I don't especially like someone waiting for me to enter a tip amount into a keypad. I imagine others feel similarly. The US isn't unique in having tips but in the UK, for example, they tend to put 10% onto the bill automatically.

ADDED: And you needed new devices but not mobile systems to bring to the table.

However the US is unique in not paying waiting staff minimum wage, which makes tips a whole other thing.

Other countries have already done this (e.g. Canada). So it's really only about the money and not about the culture.

In reality you don't even need to sign the paper. You will still get charged and the signature is irrelevant

Still seems slower than entering a pin on a number pad.

Also why are scribbles equatable here, they are very subjective to verify.