Last time I used my Diners Club card at a restaurant was at California Pizza Kitchen. The server took the card away, fought with the POS/terminal for a minute and then came back and asked me to go with him to the takeout counter to run the card there.

Another experience early on in my Diners Club ownership was also similar. The server once again took the card and then came back and told me that it was asking for the PIN. I had to go to the back of the restaurant to enter it.

Altogether, I've only had someone come to the table with a wireless card terminal once in the US. The rest of the time was either like I described or was a place like Denny's where it was expected to pay at the front. I mostly just use my chip and signature cards at restaurants now because of this (and also because DC's rewards aren't good enough to consistently deal with the hassle), even though chip-enabled restaurants are still pretty uncommon. I'd probably think differently if wireless terminals were more common or if we more consistently had to pay at the front.