Unhappy people with child often "surprised" by totally expected things.

It's probably an overgeneralization, but I often come across people (offline and online) who turn into just a parent. Especially in our patriarchal society, women will have their lives mostly devoted to being a mother and losing themselves in between, while overworked and tired. The father complains that the wife is changing and that the relationship no longer has spark, hello? She is tired and robbed, and on top of that, you are the closest person, how can you not understand this and the outcome of both of your decisions?

It's alright if they are aware from the beginning, but it seems they aren't and then get surprised afterwards. Nothing surprising about the overwhelming effort of taking care of another human being while staying afloat in this economy, let alone it's built on a non-solid relationship.

I just can't wrap my head around it. Why don't they know? Is it because of a lack of real-world examples? (I have a lot of nephews and nieces, so I witnessed how hard it is to be a parent), Is it because irrationality also plays a part in how humanity survived? So it's our brain that tricked us all along?

I'm not trying to diminish their experience. It's hard, and we, as a society, need to provide better support for child support, but at least don't act so surprised by the obvious things.