Having children and not taking care of them is in very poor taste. We see it all the time where people become parents, yet continue to focus on themselves rather than sacrificing their wants to focus on the needs of their child. It's easier to see how people would be less willing to sacrifice their time to take care of a parent that did not sacrifice time to raise them.

Sure, maybe too much of a drive by comment for this esteemed body of learned readers (ha!), but I'm just pointing out a possible source/cause of the cycle.