Just quibbling here:
1) There's no meal service on Domestic US flights in coach, anyway.
2) Transcontinental domestic US flights can last more than 4 hours. For example, Baltimore to either San Francisco/Oakland or Los Angeles takes about 6 hours westbound, 5 hours eastbound. I expect a flight like San Diego - Boston would take even longer. In addition, many fights are actually longer than that because not every city pair has non-stop service, so you will need to add the waiting time in the transfer airport, not to mention some pretty weird routings, like flying from Baltimore to San Francisco via Dallas. Of course, if you do have to change, you can buy and eat your meal at the transfer airport.
3) Do airlines provide meal service in coach on flights to Alaska and Hawaii? The are domestic, but depending on the route, it's possible some flights could be of equivalent length to overseas flights. How about flights to U.S. territories like Guam or Samoa? Are they considered "domestic?"