For most of the year I'm more than happy with my decision not to have kids. But then the holidays come around and I want to send out cards and realize I can't because somehow this has turned into a thing that only parents are allowed to do.

It didn't used to be this way. It used to be that people just sent regular cards and if they wanted to stick in a snapshot or some school portraits of their kids that was a perfectly fine option. But it wasn't standard. It wasn't de rigueur. It wasn't the...