If a man seduces a virgin who is not betrothed and lies with her, he shall give the bride-price for her and make her his wife.
Marriage is important. Most of the Old Testament Law is what we call “case law,” giving us examples we can then apply to our own situations. We see in this law that there were no such things as “deadbeat dads” in ancient Israel. Once you had slept together, you were married. It is a big deal. The move towards thinking that sex is just a physical act is misplaced. It is out of step with God’s Word and with the reality of who we are. If you’re willing to sleep together, you need to be committed to each other for the rest of your lives. That’s how it works. Do it any other way and you’re hurting yourself and others.