Why you’ll leave a tip — whether you want to or not

David Mitroff’s favorite restaurants in New York and San Francisco now quietly add an 18 percent tip to his final bill — before he even has a chance to consider a gratuity.

Automatic tips have also appeared on his hotel bills and when he checks his luggage with the airport skycap. It’s almost as if everyone assumes he wants to tack a few extra dollars onto the final tab, even when he doesn’t.

Get smart. Sign up for the newsletter.