You Can Usually Only Equalize Downwards
The problem with trying to equalize is that you can usually only equalize downward.
If you are going to try to equalize the chances of women getting jobs as firefighters then you are going to have to lower the physical requirements of height, weight and upper body strength. That means that you are going to have more firefighters who are not capable of carrying an unconscious person out of a burning building.
If you are going to have these lower physical requirements be the same for both women and men, that means that you are not only going to have women who are not capable of carrying someone out of a burning building, you are also going to have men who are likewise incapable of carrying someone to safety.
Most activities do not exist for the sake of equality. They exist to serve their own purposes-- and those purposes are undermined, sometimes fatally, when equality becomes the goal.