I'm a strange individual. I never thought anything has changed between my friends and I because of marriage as well as children. I also don't pay attention much to how I think how my friends who are married, single, childless (or childfree if they never want kids ever), and parents should be. I guess the reason for my lack of expectations and not giving it much thought is similar to when you asked about women wearing pants to a wedding almost.

The reason is I just don't think about it because I'm a strong individualist. I vehemently believe in the philosophy of "Live & Let Live" where I let people live the lives they want to live while I live mine the way I live (which does factor into individualism a lot impo). Then, with individualism itself...I believe that everyone is different in their own unique and special way, so I don't expect them to go along what the rest of society expects of them if they are a particular martial status as well as have kids or not.