Why do most commercials for universities, college or schools feature only female actors?

Hello,

This question is not biased for anybody, i just want to know why many (most) commercials/ads for educational institutes (on TV, banner board hoarding, newspaper or on websites) feature only females actors?

I can’t name any but you must’ve seen such ads many times. The reason can’t be what i am thinking! can it?

Please explain if you do know it..
Regards!