To each, their own.

I am usually warm even in long sleeves, so wearing a jacket can be incredibly uncomfortable for me--since most restaurants are at a temperature that is great for most people but too warm for me.

I'm gay and love to dress up...so I desperately wish I could wear a jacket, since they offer such a great chance to snazz up an outfit. But it's not meant to be for me, alas. Comfort must trump a jacket requirement for me, even being well dressed otherwise.

We also live in California...where being more relaxed and casual is a normal part of the culture, even at almost all of the finest of restaurants. We find other ways to be well-dressed in lieu of a jacket. The jacket requirement is a class standard from a time long gone to us...and to me. But that definitely is not the mantra in many places in Paris, Milan, Rome, Venice, or even New York.