There's certainly a cost to equipping terminals at every table.
I'm just talking about those little handheld things that are a little more bigger and thicker than one of those old cordless phones.
The waitress brings it over to your table in Europe when you tell them you want to pay by credit card. You can enter a PIN there or it will print out a slip for you to sign if you have a US card. But the newest ones also have the NFC chip and will show the contactless symbol on the screen. That is when I use my iPhone.
I usually tell them I want to tap or use contactless. Then they have to enter in the amount and then the contactless prompt comes up.
Anyways those little terminals are maybe $200 at the most.
A lot of small restaurants may not be able to absorb that cost, especially if they need to get several of them.
But my suspicion is that many banks, especially in Spain, will lease or provide those terminals, just so you end up using those banks to clear the transaction, for which they get a fee.
So I contrast that with Austrian and German restaurants who want cash unless the bill is at least 20-25 Euros.
In Spain, a lot of my bills were 11-12 Euros (and they were some of the best deals, good 2-3 course meal with house wine in Asturias).