I come from a larger-than-average extended family, and some people just like having children around, so they have kids to extend that. Or they want siblings for their kids, or simply love being a part of a large family. I can't really hate on that, because there can be a lot to like with that scenario, especially when you're in a small town and there's not a whole lot else near you in terms of other kids to play with.
My dad was 1 of 7 (3 brothers, 3 sisters), and my mom was the youngest of 5, all 4 siblings were older brothers.
On my mom's side, there's only 4 "grand kids": Me, my younger brother, one older cousin, and one adopted older cousin.
On my dad's side, there's 19 "grand kids", with all families having at least two, and one family having 5. They would have had 6 if they didn't lose 3-4 of the last pregnancies in a row.
In 3 of those familes, they wanted at least one girl. One had a single boy, then stopped when they had a girl. Another had three boys in a row, then threw in the towel. The family of 5 above, their 1st was a girl, then all boys. They saw how the boys bonded with each other and wanted a sister for their oldest girl, so they tried for another daughter. All of those subsequent (lost) pregnancies were girls.