Yes, it is more acceptable to have children after marriage, but 50% of marriages end in divorce. So that works both ways. Marriage is a catalyst for having children, even though it has been shown that marriage itself is not an ideal condition for having children in the first place.
I'd say it's better if people need to be more cautious. Choosing to have a child with someone would require a legitimate trust, instead of a legal based trust, which is almost like saying "I do trust you, but... just to be safe...". It's a step up of responsibility that people need to take in order to be less reliant on the government to do everything for them.
Same idea with property.
We have a fucked up concept of marriage in this day and age though.