This came from the time it was acknowledged as fact that women are physically weaker than men and in certain situations may need physical protection. Normal healthy males are protective instinctively it's in their nature it might be hidden deep down now because society has deemed it sexist to show this trait.
Would it be safe for a female firefighter to carrry an adult male down six flights from a burning building?
Children are smaller and weaker than everyone and need protection ALWAYS full stop.
Once upon a time a woman or a man would die to protect their child.