I've often thought this same thing OP! However, I don't fit the profile. As well as I ate and took care of myself, and my wonderful midwife as well, my daughter only weighed 5lb 9oz at 38 weeks. She is still tiny, which is unusual because I am a tall woman, and her dad is not a small guy either. She's our little peanut!
I secretly desire a huge chunky baby though - I was so jealous of my friend's 11 pounder!