Why do people feel the need to put a damper on a kid's creativity?

I was waiting to get my nails done and this woman was there with her daughter who was about 6 or 7. The little girl asks if she can get her nails done and her mom tells her to go pick out which colors she wants. She sent her back like four times telling her those colors weren't acceptable or whatever. Why? Does she think people are going to look at her kid's nails and me all "Woah Barbra! Yellow and turquoise? Why would you let her do that?" It's nail polish not a tattoo.