Yes, parenthood is hard sometimes. But really, so are a lot of things that bring rewards. You don’t have to tell a parent about the rewarding part; a parent is living it. But the feelings of joy and fulfillment that come from raising a child are hard to describe or to express. Partially, perhaps, because people feel bad about expressing them, because everyone knows that non-parents don’t want to hear you get all googly eyed over your kid. People complain when parents complain, but they complain about parents kvelling, too.
It seems like non-parents mostly want parents to just shut up already.
Acknowledging the difficulties should me a way for parents to find support, both personally and culturally. But even if it’s not, I don’t think parents should have to be their own marketing department. As far as I’m concerned, my evolutionary imperative does not extend to the species at large.