God had to tell Abram to take his wife Sarai and all his household and worldly goods to pack up and leave. Otherwise, he’d have stayed in Ur of the Chaldeans. Moving away from all your family is a modern phenomenon.
What about the girls? Should women be shown the door at 18? 21? Not until they’re married or join the convent? What if they do neither?
This is correct. Nations started as PATRIARCHIES, (hence the Jєωιѕн propaganda of feminism against men "the patriarchy"). After all Adam being the head of humanity is a male. When groups of families led by men join together you get small scale nations etc. I don't think I need to explain this since I think it's self explanatory. They make rules and agreements and bind themselves to those rules in return for things like supporting each other, food and trade, marriages etc.
Frankly when the economy gets bad it's the men who marry later not the women. Hence why Aristotle mentioned the ideal age for woman being 18 for marriage while for men it was 37. Because the male is expected to provide, the woman can just marry an older man, she doesn't need to wait to get older. Put it this way, what difference is there between a woman at 25 marrying a 35 yr old man or a woman at 18 marrying a 35 yr old man? In both cases the man is 35. Unless the woman is also working what is she waiting for? Maybe she is more comfortable with a smaller age gap? But that could be due to modern propaganda, also marriage requires self sacrifice.
So in my opinion, the economy being bad doesn't effect the woman's marriage age unless she also wants to be educated and work (female education is the #1 reason for delaying marriage).
Girls never leave the household of their father unless they become religious or married. It was scandalous otherwise.