I agree about not wanting to save 20% on a restaurant tab when I am on an expense account. But if you join transmedia or an airline's dining program and get 10 miles per dollar that adds up. Also the transmediacard.com/DALC.com websites have some menus for places in cities so you can get a heads-up before hand.
On some trips I've earned more miles on meals for some trips than from the flights.

BSL