Car seats as contraception is just a specific enumeration of the general. "busybodies as contraception" problem wherein the "has so few real problems they stop minding their business and mind other's business" classes try to force priorities on the rest of society that the rest of society can't yet afford to have. And it's not just contraception or kids. Pretty much everything in our economy gets shot in the foot by this to some extent.

It’s not the car seats that are the contraception, it is the cars themselves.

I actually thought about including this in the piece (and how car sizes become a problem once you hit 4+ kids) but decided to keep it more focused on just the healthcare costs