Spiritually speaking, if you believe that you should have sex prior to marriage ...?

Because they never had anything else. If I've only ever been on one rollercoaster, and I was committed to that rollercoaster it would be the greatest one in the world, but if I've been on many rollercoasters than that rollercoaster I've committed to might be extremely dissapointing. And arranged marriages are made by the parents and they stay together because they have to, I'm sure there are very few happy couples in arranged marriages.