Just friends

Why can't male friends  remain just friends? What is so hard about just being a friend? We just can't have a reasonable friendship that is not sensual again? Male friends need to understand that there is more to friendship than sex . Today, you start talking to someone, he sounds smart, and you think you have met someone that you'd learn something from, and him in turn learn a thing or more from you, but he spoils it all by trying to have sex. We really can be friends without going that way. Don't just spoil our friendship by trying to have sex.