While this isnt true in 100 percent of cases, most women dont generate muscle mass because it is more important for them to carry fat on their body. For example, if a man and a woman both do the same workout for 5 months, the man would show more dramatic muscle gain, while the woman would stil appear smaller in comparison. The woman may be just as strong, but the muscles don't appear as massive because fat wouldn't have the space to sit below the skin. Women needed fat in the past because they have to expend some of the energy they gain from food to nurse their children. They also use it to keep their insides warmer for their possible baby.
Hope this helped
