What is the main reason for having premarital sex?

Answer I can only answer from personal experience but what would happen to the two of you if you waited until the two of you were married before you had sexual encounters and you find out that you aren't sexually compatible? It's not every man and woman who are sexually compatible so it's like going to a store to buy a coat. Would you buy it without trying it on, not me, I'd want to see if it fits perfectly, you should too.