Long hair is supposedly sexually attractive because it's a sign of good health. One must be healthy to grow long shiny hair. I assume it is not in fashion for men because it could be a hazard in hand to hand combat. That being said, some warrior cultures allow their men to grow their hair (greeks, native ameircan etc..).
I have studied the Bible and the theology behind Christianity for many years. I have been to many churches. I have walked the depth and the breadth of the religion and, as a result of this, I have a lot of bullshit to scrape off the bottom of my shoes. ~Ziploc Surprise