Back when computers were actually expensive and wireless networking technology wasn’t as good/common, they would take your card to the back office and run it on the single, hardwired card terminal.
Nowadays it’s less of an issue as those terminals cost peanuts and WiFi is ubiquitous so they have many of them and can just bring one to your table.
When there was only a single terminal it was common in Europe to just... walk to the counter and pay for the meal card in hand. No other way to type in your PIN
Not universally true. I had a couple of cards without a chip because, reasons. I still was walking to the counter myself, because giving somebody my card feels weird.
I was having lunch at a hotel bar in Vegas a number of years back. A Brit, I think, was paying for his meal and he was like "why are they taking my card???" So I explained. In my experience in the UK, they don't want to even touch your card.
Nowadays it’s less of an issue as those terminals cost peanuts and WiFi is ubiquitous so they have many of them and can just bring one to your table.