Tradition and ideological homogeneity was much stronger back then.

The world was simply much simpler.

The number of practically available paths forward were less. So why wait? Nowadays people are in an analysis paralysis, so they just wait. (Or try to find better mates, better jobs, better social groups/communities, move around more.)

And due to less homogeneity it's seems harder to find someone. (And probably is harder.)

Also the acceptable mortality was higher. Wars were more common, losing people due to illness was also more common, etc.

And nowadays we have endless alternatives to getting married. Single life is very enjoyable. (see Netflix et al :))

If look back at the society of the past from where I come from, this is the same society that gave us Jim Crow. Before that, chattel slavery.

Not really sure what I'm going to be learning from them about raising children in the 21st century.