That said, I'm with you; I much prefer to have my card handled just once and within sight. It is faster, safer, and, to my mind, simply more convenient.
And that is considered "cheap"! By contrast, in the European Union there's a cap of 0.3% on credit card interchange rates and 0.2% on debit. Of course that's just the raw interchange fee; a small merchant has to pay more than that to its card processor, but there are all-inclusive, Square-like offers for debit card processing fees below 1% for small merchants, and larger ones manage to keep both debit and credit processing cost way below 1%.
So the "comfort" of being able to hand over your credit card to someone who takes it out of view and possibly does unauthorized stuff with it increases prices of all the stuff you buy by roughly 2-3%.