I'm not sure it has to do with maturity. Full disclosure, I'm generalizing below. 20-25 year old women won't date 20-25 year old men because most men are broke at that age. Men start earning enough to date somewhere between 25-35 years old and they date women 20-25 years old because those women seek older men (that have enough money to date). That cascades up though the years. I didn't start dating regularly until I was 30 because I didn't have a good enough paying job.