They are not. You are presenting a false premise. There are not specific “don’t have more than two children” messages being baldly promoted, but the awareness of overpopulation is high, and most of the subliminal messages in our society indicate that having one or two offspring is the norm. In fact, in normal conversations, if a couple has three or more children it is now considered to be a lot, as opposed to when I was growing up and most of my peers had at least two, often more, siblings. Maybe if you live in a fairly rural area, this doesn’t apply as much, but families are definitely shrinking.