It is a man's duty to have children. Two. A boy and a girl. Enough to bring hope for the future. If a woman is barren, there is that much less reason to marry her. Certainly that would be the main consideration if a man is allowed only one wife. So it was great to Samuel that his Dad could have multiple wives, for his own mother was a barren woman, and if polygamy was not allowed -- divorce, then no Samuel.
1 Samuel 1:6-7
6 [This embarrassed and grieved Hannah] and her rival provoked her greatly to vex her, because the Lord had left her childless.
7 So it was year after year; whenever Hannah went up to the Lord’s house, Peninnah provoked her, so she wept and did not eat.
Polygamy is a wonderful thing.