Why do people think having parents who are "younger than usual" is embarressing?

I'm 15 and my mom is 27(she had me when she was 12) and all I ever hear is people tell me that I should be embaressed of having a mom who is 12 years older, once I even heard my moms backstabbing friends say I'd most likely get made fun of in school for having such a young mom. I just don't get it......how exactly is that supposed to be embaressing or something to not be happy about? I for one loving telling people that my mother and I are only 12 years apart.