Why is there etiquette if people don't know the rules anyway?

Planning a wedding really teaches you a great many things. Aside from the obvious: save money, plan ahead, and have fun with it, but don't go too overboard with the planning--does one really need 100 white doves released at the conclusion of the ceremony? Or a chocolate fountain for fondue dessert? There are many things you learn about your family and your family to be--and maybe even your friends.

Example number one: Ecstatic parents who want to parade around their children at the wedding, forgetting that it's not a dog show, but a wedding. If the save the date or more important, the invitation, is not addressed to "The _____ Family" or doesn't list the children's names on the envelope--they are NOT invited. It was NOT an oversight on the bride and groom's end to omit these names. We simply didn't FORGET to put their names down, especially when the bride HANDwrote each and every save the date envelope.

Example number two: I don't have one yet, but there's time.

So in closing, why is there etiquetee if people are going to be ignorant, selfish, and self-centered? You really bring out the bridezilla in me!