I think it's because God wanted us to see what love between a husband and wife should look like. In my Bible (true Images) every book has an intro to it. Here's how my Bible answers the question:
On one level, this song celebrates that God created sex and wants married couples to enjoy each other. On another deeper level, it pictures the overwhelming love God has for his people- faithful, true, unending, joyous.
I think this is exactly why this is in the Bible! Anyway, the reason I'm writing about this is so I can pick apart part of this book. For the next few posts, I will be (trying to) explain Song of Songs 4:9-15. Hopefully, with a lot of prayer and studying, I will be able to.
Well, time for bed. 'Nite readers!
Black Swan