I agree that SAHM/SAHW is not a job, persay, but it is an important role in society.
I volunteer at the animal shelther, and I wouldn't call it a "second job." It's something I love doing, and do for the personal gratification it gives me. I see being a stay-at-home homemaker the same way. It is (hopefully) personally gratifying for those who choose to do it, it contributes to society, it's important to those who rely on it, but it's not employment in the strictest sense of the word.
For what it's worth, my DH and I are saving as much as we can so that when we do have a child, I can stay home with it for a few years. I may try to do freelance work from home after half a year or so, but I guess it all depends on how we feel at the point. I would argue with anyone who denigrated my choice, as we are working hard now to be able to afford it, and I don't see why anyone else cares what I choose to do with my time.