Why a father cant replace a mother?

A mother can always put her child's hunger before her own.
A mother can sense what the child is feeling even before the child expresses it.
A mother can easily change the mood of her child.
A mother mostly knows the child's needs.
A mother knows when to pamper and when to control her tantrums.
A mother can sense the pain the child might be going through.
A mother can never be happy when her child is suffering.
A mother may not know what is best for her child, but she will try to give her best at motherhood.

I am not generalizing here. There may be cases when fathers' replace mothers' and every case has an exception.

However, a father makes a family complete.