It's not only through pop music, but pop culture in general. We're always bombarded with this stupid idea that having kids is just "what you do" - that it's not a choice. Last night, I happened to hear a little bit of Entertainment Tonight after finishing watching something on the DVR, and they were talking to Kim Kardashian, who is one of those celebrities that is famous for pretty much no reason other than being rich or something, and she said "Of course I want to get married, have kids, you know do all that adult stuff...".
Stuff like that irks me. It's like everyone is supposed to just follow the same path in life, when we know that's not the way it is for every person.