The conventional answer is, "Because it was there." My gut reaction to that answer, though, has always been, "That justifies nothing."
In that light, I enjoyed hearing Al Jarreau's "Closer To Your Love" come up in iTunes shuffle mode today. In addition to its appealing vocals and energy, the tune's lyrics turn the cliches of saying you'll climb the highest mountain or swim the deepest ocean for someone inside out; in essence, the pursuer's point of view is, "Why can't I just say I'm interested in you? Why is it necessary for me to exhaust myself to prove how I feel to you?"
That's some of the most refreshing candor I've heard in any song.