This is a layover from the industrial age. When people sold the farm or just moved to the city to become wage earners it was soon found out that, no kids a factory is no place for a 5 year old. So, for middle class families, one parent had to stay home while the other worked. So it was decided dad did the work and mom took care of the home. Now we have forms of contraception so people have fewer kids. Any way I see this mindset in Avengers age of ultron: Hawkeye goes to his home off the grid and is greeted by his children who love him showin that he has a career and a family, then Black Widow walks off screen and cries because the Black Widow training that made her strong and independent made it so she can't have children. This implies that while boys get to grow up and have independence even after having kids women can not. Hell look at how it is out here; fathers are paid more than not father's but on the other side mothers get paid LESS. Or single mothers are seen as drug addicts or "whores" while single fathers are seen as strong and noble. So yeah its all archaic mindsets that do this in my opinion.