Parenthood creates a unique dichotomy: it is very, very difficult, but extremely rewarding. I have never had a harder job. It's hard in the early months, especially. As the baby grows, old challenges disappear but are replaced with new ones (mobility, handling emotions, etc). But along the way, there are things that make it worthwhile, like breastfeeding, being able to play with baby, teach baby, watch her develop into a little person, etc.

The jobs you listed are not as difficult because a) they all pay $$$, and b) presumably one does not have to do them in 24-hour shifts!