Not entirely correct. We are finding that in more and more restaurants - perhaps in most - if we ask the server to add the tip to the bill BEFORE they take the credit card, they are agreeable. Some hesitate but then agree, and some still say "no way."
U.S., allies conduct 22 strikes against ISIS targets in Iraq, Syria (Reuters)
from the article: Tourist tip #32 / You can't add the tip to your credit card