I believe that a bit of unfamiliarity with your fiance leads to a certain mild formality in the early years of a marriage. That formality leads to a bit more careful politeness. Good habits of plain old courtesy go a long way towards a peaceful everyday life as a marriage matures. That courtesy is more natural when, as you and your spouse are beginning your marriage, you aren't as familiar to each other as the dirt under your fingernails.
At the time Mad Musician and I married, we had known each other for 10 months. Many of those months were months that I was spending 40+ hours per week in upper level architectural studio; he worked full time and lived an hour away. Nearly all my friends and aquaintances thought I was bat-poop insane to be marrying "so young" (I was 22) and without a trial period of living together to "make sure we're compatible."
The essentials lined up, though: we shared a common faith, a common approach to financial matters, had come from families of similar backgrounds. We shared a love of Bach, church music, and cars as well. And most importantly, people who knew both of us really well thought we were a good match for each other.
But at the time we married, we didn't know each other all that well. We weren't familiar with each other. That bit of unfamiliarity meant we were more polite. We were guests in each other's personal spaces, in a lot of ways. "I'm going to take a shower, did you need the bathroom before I get in?"
There are numerous reasons I don't believe couples living together before marriage is a good idea. The religious reason is only one of the many. This is another. The early days of living together set the tone and the habits for later married life, but the habits set during living together are habits and ways of interacting that have as their backdrop the relatively easy-out of simply breaking up and moving out.
Better that those habits, those ways of talking together, shopping, dealing with anger, picking up dirty underwear, and sharing a bathroom be formed when a couple is still a bit "shy" of each other and in the context of a commitment to working at a permanent, difficult-to-dissolve, long-term relationship.
I also believe that what I've outlined above is one of the reasons that arranged marriages have such a high success rate.

