A Half(Lie) is as Good as a Whole
To protect his own life, he asked Sarai announce their birth family relationship, not their marriage relationship.
A brother could be made rich with bride-price. A husband would be merely in the way.
And an ancient Egyption despot knew how to deal with people in his way. (And what were they doing in Egypt anyway? They were supposed to be in Canaan, famine or no.)
Maybe Abram hoped nothing would come of this. But it wasn't a good situation for Sarai. She became essentially imprisoned as a junior concubine in a harem when she was accustomed to being queen of her own household.
Did she live in an age more miraculous than our own, or did it only seem that way?
We are in awe of the way God protected her in an obvious way, not once but twice, preserving her unique position in the royal lineage.
SUCCUMBING TO THE PATRIARCHY, OR TRUSTING GOD?
He was ready to sacrifice her for his own life. We are scandalized, but, within the bounds of their culture, it was simply a natural, obvious decision.
In a society where the husband's primary duty was to the patrimony, with himself secondary and his wife not at all, it was amazing that Abram had not long since taken another wife.*
But what about us? Our culture is different, isn't it? People are more valued than inheritances, at least in theory.
A marriage should be a place of mutual protection.
A man should not put his woman in danger. But he should be able to rely on her.
And it works the other way, too.
Maybe some circumstances really do demand this degree of sacrifice from a woman. i'm not qualified to be arbiter of circumstances i'm not privvy to.
Did Sarai hold her tongue? From the other things we know about her, i'd guess not likely. But she stood with her man.
And Scripture is plain that Abram was in the wrong by asking this of her.
God doesn't always visibly hold everyone accountable in this life. And "taking care of us" may mean "through," not "rescued from."
But accountable for sin and taking care of His own, that's still true.
*the Reformation Study Bible Commentary is helpful on this: Genesis 16:2, Genesis 16:6