Why did Lot's daughters seduce their father?

According to the Genesis 19:30-38 , when *Lot* escaped out of *Zoar*, he went up to the mountains and settled in a cave. While in there, his daughters seduced him while he was drunk so that they could bear children and save their family line. Does this mean saving one's family line is/was so important that you could have sex with your own offspring? Was Lot really drunk to a point that he didn't know what he was doing? Were the daughters wrong to do it? If so, why didn't Lot take any action afterward?