Dear Etiquetteer: This question came up at a work dinner. I was served first, as was one other person. As I was taught, I waited for others to be served. One other told me to eat while it was warm. It was then mentioned that the new etiquette is to eat when you are served. So what are the rules? Eat when you are served, or wait for others?
Etiquetteer's first response when reading your query was, alas, rather sarcastic: "Have you heard about the new etiquette? You get to do whatever you want no matter how inconvenient to others!"
Why do we wait for others? Because it's awkward to be the only person at the table not eating, whether that's at the beginning of the meal or the end. We are invited to break bread together, not consecutively. Suppose you had bolted through your dinner and had nothing left by the time everyone else was served? You'd be in the same boat as the diner who had been served last. It's equally awkward to be the last person still eating.
When dining in a private home, everyone's dinner is more likely to arrive because everyone is (more often than not) being served the same meal. When dining in restaurants there is always the risk that diners will be served at different times, because the cooking times of individual choices may vary.
It's most Perfectly Proper to wait for all to be served before beginning one's meal. It's most Perfectly Proper, when one is one of the last to be served, to exhort others to begin eating - especially if there seems to be a risk of a lengthy delay. And even when urged to begin, Etiquetteer does so with reluctance, hoping that the waiter will really not be too long with the remaining covers.