That was true before the introduction of chip cards, though. The waiter's having to carry the card to the staff area of the restaurant, complete the transaction (by swiping), then return the card to you, probably interweaving some of their other duties along the way, took up most of the time. Their having to wait an extra few seconds for the chip reader seems a drop in the bucket.
I noticed this process has gotten noticeably longer after chip cards where required.
Waiters used to take cars and swipe them ASAP presumably to get better tips by being prompt. Now, put this off until they finish a full round and/or put cards in and start doing something else because it's going to take a while.
Granted, this is far from a complete switch, but it was still noticeable.
You don't have to hand anything over with near field stuff. You put it near it, ding, done. Saving you 5 minutes + time it takes for you to exchange cash. If you're dealing with a waiter for lunch, you're already wasting a ton of time.
In that case cash can save ~5 minutes.