Sex should only take place between two consenting adults. If someone does not want to have sex then they shouldn't allow themself to be talked into it, pressured, or give in due to an ultimatum.
Having said that I personally could never marry a woman I had never had sex with. In my opinion you can't manufacture chemistry. It's either there or it's not. One of the top reasons people give for cheating is sexual incompatibility or lack of passion in the relationship or marriage. It's a romantic notion to believe a man or woman who has never had sex will suddenly become a "super stud" or "lioness" in bed after saying "I do"
Sexual compatibility for me is (just one of several items) on my "check list" to determine whether or not there is a possibility I could spend the rest of my life with a person. Awhile back I wrote a hub on it's importance.
Keep in mind everyone is entitled to have their own list of requirements! Ulitmately each of us is looking for someone who "naturally agrees" with us.