It's sometimes a cultural thing. When we were in Eastern Europe and Spain/Portugal (maybe Italy as well??) a majority of baby girls had their ears pierced as they do it so you can tell they are girls and not boys. I can remember walking around London with one of the gorgeous baby girls I nannied for, she had on a dress and light blue cardigan and a Spanish shop keeper thought she was a boy, I corrected him and he said that because her ears weren't pierced he assumed she was a boy. It's also very common in Latin America.