I'm not going to rub your religion in your face, I don't think there's anything automatically wrong with religion just for being religion. However, religion allows for a lot of things that make no logical sense, and the marriage issue is one of them.
Obviously people can have sex without commitment and commitment without sex, and either one of those things with or without marriage. To argue for the sanctity of marriage in a country where Kim Khardashian can be married for 72 days (or Britney spears for 24 hours, anyone remember that?) is obviously retarded as well.
There are many religious couples that live with commitment and no sex, and many couples that have sex all the time with no commitment to each other. They are obviously not mutually exclusive and there is no logical correlation between the two. I don't understand why holding off on sex is a requirement to prove one's commitment, especially when, as you yourself stated, "intimacy is an extremely important factor of a long term relationship, and if something doesnt "work out," and you dont learn about it until you're married, that can ruin the whole thing."
There is no way to know how many marriages have been ruined due to those issues. And furthermore, it is an ABSOLUTE FALLACY to assume there would be fewer cases of unplanned children or STDs. The only way to decrease these is through education and safe sex practices, or through people simply having LESS SEX, not less UNMARRIED sex.
Frankly, and I'm just being real, the majority of "religious sex abstainers" I've known had no clue about safe sex or birth control, or their religion PREVENTED the use of birth control. I have known religious couples who had unplanned children because of their lack of education about birth control, and committed celibate couples that have passed on STDs they got through non-intercourse means like at a hospital or simply making out with a sick person.
Be ethical all day long if you want, but there is only one thing that will ever increase your preparedness for anything, and that is education. Also, admit that commitment, sex, marriage, and love are NOT consequences of each other nor are they reliant on each other.