Of course the Bible says that sex outside of marriage is a sin.
But we know that sex is a major issue that can make or break a marriage. It is important for people to know what their partners like and don’t like in sex, and how much libido their partners have. We know that a marriage that is not open to life is also a sin, in Catholicism. We know that lack of sex, or bad sex, can ruin relationships and destroy marriages.
So practically speaking, despite what the Bible says, don’t people need to “test drive the car before they buy it,” in other words, have sex before marriage to test each other’s sexual compatibility? Isn’t it a foolish risk to not “test drive a car before buying it?” Wouldn’t it be a possible setup for failure to not have sex before marriage?