"You shall be holy to me, for I the LORD (Yahweh) am holy and have separated you from the peoples, that you should be mine". Lev. 20:26. Part of being holy is being different from the world around you in moral conduct. God separated the Jews by making them his people and giving them the law that separated them from the world. God is different that the world, so they were to be different than the world and reflect God's moral character.
Peter applied the concept to the church. He wrote "But as he who called you is holy, you also be holy in all your conduct, since it is written 'You shall be holy, for I am holy.' " (1 Peter 1:15) He affirms that the church is separated from the world, called out, as was Israel, and is to be distinguished from the world by moral conduct, as was Israel.
Paul spoke of being transformed (into the likeness of Christ), not conformed to the world. (Rom. 12:2) When we look like everyone else, we do not witness to the world of God's great character.
The additional blessing is that God meant his moral law not just for his exaltation, but for our happiness. Deuteronomy 6:24 says "The LORD commanded us to obey all these decrees and to fear the LORD our God so that we might always prosper and be kept alive."
America has forgotten that. Much of the Church has also. I am grateful we have the book of Leviticus, for it teaches us that God knows what is best for us and, if we obey his plan, we will enjoy His favor and His blessing.