For FR it's this equation:
Christian upbringing and teaching on relationships = nonsexual approach to women and dating = loneliness.
I look at the former as part of the basis for the latter. It's not limited to Christian upbringing, really. Honestly I think a lot of messages sent in our culture undermines a man's willingness to be a sexual creature. Some of it comes from very religious foundations of all flavors, and a lot of it comes from the very bad messages women (and our culture) sends to men regarding 'what women want.'
I love my mom a lot, but if I listened to her advice on courtship, I'd never have a second date. Women, for some reason, perpetuate the bad messages being sent to men on how to behave in a sexually appealing way.
For me, the cardinal offender is the idea that women somehow want a nonmasculine male. That makes no sense and hasn't much evidence to support it, yet every time a man camoflauges his sexual nature around a woman, it rears its ugly head. The result is too many frustrated males and too many unhappy women.