Why are people so obsessed with procreation/having kids?

To me its almost like a cult-like mentality. Hell, one of neighbors the other day took out a 100K home equity loan to help pay for medical expenses to help her get pregnant........disturbing. I mean she doesn't live on a farm so she doesn't those "farm hands" to survive.....I just don't get it. Why are people so obsessed with procreation/having kids?