Very good point, Katie. I was just thinking about this today. Just b/c parents complain doesn't mean they don't like being parents overall. I just know I would hate it, and the positives parents speak of just don't appeal to me. My bad days at work, though, end at 5 p.m. I don't have to continue to make dinner and bathe someone that has been mouthing off to me all day long. And, if my job gets to be too much, I can get another one.
Another thing no one seems to talk about is how our life interests change. I can only speak for myself, but I know that if I got married in my early 20s I would have picked someone very different than my fiance. I also changed my major several times. I wonder if this happens with parents, too? They want kids, and they do it for six years, of whatever, and want to do something else, but they can't? I know that I like short-term projects in work and life - there has to be an end in sight. I like to check it off the list that it is done. You are never done when you are a parent. You could argue that the deliverables change in the parenthood project, so that someone doesn't get bored. But what if they do? And they tire of it?