It is a recent invention that has us all confused. The rush to validate the gay rights movement has pushed people far beyond their comfort zone, and the culture war has put pressure on people to assert their allegiance to the camps by overstating or denying their deep connections. "I love you bro" was actually a pretty common sentiment, and now many very progressive people feel the need to qualify it - "I love you, bro, but not like in a sexual way, not that there's anything wrong with that"
Lines have been blurred and confused and nobody's the better for it. It is a shift in religion that caused us to lose our knowledge of how to love someone as a friend.