Why do so many people judge someone who decides to be abstinent?

I have nothing against people having casual sex. Do what you want, it's your life and your body.

Personally, after a large handful of casual partners and being single for the past 6 years, I've decided I want to remain sexless and single until I finish school and move out of my current state (Florida).

My friends who are older (50+) think I'm wise for doing what's best for me, but peers of my age group are so harsh about it. I've had women ask me if I just can't find a man to sleep with me, and I've had men who see me as a challenge to overcome. Not desiring casual sex is never enough of an answer to them. I'm so tired of hearing how wrong I am for waiting until I have a relationship instead of 'living up' my youth and sleeping around. It doesn't make sense; I don't need sex to be happy.