The reason why Abraham decided to split with Lot was to avoid any further conflicts between him and Lot or between his herdsmen and Lot's herdsmen. If the herdsmen went with Lot and were available to be husbands for Lot's daughters, why did the daughters need to sleep with their father to produce offspring?
Genesis 13:8 - 9
ESV - 8 Then Abram said to Lot, "Let there be no strife between you and me, and between your herdsmen and my herdsmen, for we are kinsmen. 9 Is not the whole land before you? Separate yourself from me. If you take the left hand, then I will go to the right, or if you take the right hand, then I will go to the left.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.