People are male or female. Men and women are different from each other in multitudinous ways, but these distinctions can be glossed over when a desired outcome is at stake. Every child needs the balance provided by the unique characteristics of two parents who are male and female.
The masculinity of a father (authority, strength, underlying tenderness) complements the femininity of the mother (caring, always available, character-molding, etc.). Forcing a child to be "resilient" and become mature in a family that can be considered out-of-balance is not fair to the vulnerable child and bodes ill for the cociety which that child will help shape. Not always, but usually.
One day our mailman told me "A little boy on my route came running out of his house and wanted to know why he has two mommies instead of a mom and a dad. He was crying. I said, 'Why don't you ask them?' but the little boy said "They won't tell me." What is sadder than that?!