[TrnsltLife]

Incest laws weren't given to Israel until Moses and the Exodus.

As for meaning:

Lot was date raped by his daughters. It shows the moral corruption of Sodom had affected his family.

It's also a historical and genealogical account of how the nations of Moab and Ammon began. Abraham's nephew Lot, and his daughters, though originally close family to Abraham, became the progenitors of nations that later oppressed the nation of Israel.

36 So both of Lot’s daughters became pregnant by their father. 37 The older daughter had a son, and she named him Moab; he is the father of the Moabites of today. 38 The younger daughter also had a son, and she named him Ben-Ammi; he is the father of the Ammonites of today.