I remember being mind-blown on my first trip to the US when a taxi driver took my card and literally carbon copied it manually (with a pencil and carbon copy booklet) on the spot.

I had been using my credit card for at least a decade (Europe) and it never ever occured to me that the embossed letters had any function other than aesthetic.

And the cheques... jaw drop

That is how they used to work though. I’m old enough to remember imprinters, which literally used the embossed numbers to create a carbon copy: https://en.wikipedia.org/wiki/Credit_card_imprinter

I had a food delivery guy use one in the US 2012/2013. It was like seeing a native tribe perform their traditional dance. It still blows my mind that chip + "signature" is a thing in the US. What good is a random indiscernible scribble on a tiny resistive touch screen as far as proving anything?

It's quite illegal to fake signatures so it acts as a deterrent. I can't think of anything else...

I could be wrong but I'm pretty sure it is also illegal to steal someone's credit card and use it. If you have already done that, I don't think the idea of scribbling illegally is going to warn anyone off. Chip+PIN is objectively far more secure. People used debit cards with swipe+PIN for decades just fine and chip+PIN is used in many other countries without an issue. It is just silly to keep using signature and acting like it does absolutely anything at all.

That was how things worked back in the 80s and 90s, online or chip systems were in place 20 years ago in Europe