I believe the enemy wants us fighting each other in our marriages so he actively works against intimacy. Too much intimacy and trust under God, and he is up against a battle he cannot win.
This is such an important consideration...but one that is very hard to go public with. There is a difficulty in describing what a functioning Christian marriage looks like. So in our time many of the aspects could be seen as controversial since the foundation of all intimacy is spiritual in nature...not physical.
On earth as it is in heaven.
What is intimacy? A moment by moment connection between two persons where they become one in heart.
The physical union in a marriage is there as a help to intimacy. The union itself, while physically intimate, is not necessarily causing the kind of oneness that God intended in a marriage. Not all marriages use sex as a path to intimacy.
Not everyone is looking for intimacy., at least, not at the outset. Not everybody lives from the heart....and is looking to connect from the heart to another heart. But if a person is shown what intimacy is, or can be, then I think most or all would desire to have it.
Many people have a life that is actually against intimacy. The inner man is looking for intimacy...but the outer man is too often looking for power and advantage. Men who struggle to be such in the world may have difficulty with the "how" to be intimate. But women also who see themselves as merely being a functionary in life. The Martha vs the Mary syndrome.
And then there is the periodic feeding of the flesh (for power) in a relationship that comes with being uncrucified in the flesh. The flareups of self that take away from the purity of intimacy by dirtying the relationship. What is sin to the relationship with God could be described as such that gets in the way of a marriage intimacy.
Men might abuse the authority given to them by being head of the house. A woman might do small acts of rebellion to feel in control. And one rebellion fuels the other until there is a rift created that makes intimacy near impossible.
Being broken before the Lord...being broken in the marriage. That is what ensures intimacy. A man is broken towards the Lord. Christ is the Head of every man. A woman is broken towards her husband. The head of every wife is her husband.