Because her father holds a Royal title so as his child she gets his title also . The Casiraghi children don't have titles because they have their father's last name it they were giving the Royal family last name of Grimaldi they would hold official titles of Monaco.
Hope that helps
Hope that helps

I think being a "princess", even a European princess, there are certain expectations to her outfits and one is nice hair. It's just as much a part of the outfit as the earrings, shoes etc. One example is Gwen Stefani, she can be running around in a track suit but she always has wonderful hair/makeup. It just makes one looked a little more polished. Anyways I'm glad you agree Alicia753