For Use, For Women Over 30

I have started to use a wrinkle cream. It is not to be used by women under 30.
I wonder what it is about 30 that is so magical. It's reminiscent of saying that someone 16 years of age can drive, and that 18 year olds can die for their country (yes, I'm being dramatic). I think that makes me think that this 30 is also arbitrary. Maybe I should wait.