Mostly because cedws is apparently more interested in birth rates than in tandem sales. Personally, I can't say I fault them for that and don't understand why that's a problem because, going back to my original point, they're not suggesting that people who don't want children should be forced to have children.
They're suggesting using the law the limit people's alternatives. You might not call it coercive but it's paternalistic at best. It's using the state apparatus and the monopoly of violence to limit people's choices in such a way that they're encouraged to choose to breed. I'll stand by what I said: it's creepy.