Hydraulic brakes had more leverage over mechanical. Just like air brakes have more leverage over Hydraulic. All about effort and efficiency I believe.
Sorry original poster- back to you!
Actually that is not necessarily true. The big problem with mechanical brakes is keeping them adjusted and "equalized." There's no reason, "for short periods" that mech brakes can't have the same leverage as hydraulic.
But things like the 30's Ford cars used flex cables (like modern parking brakes) on the front wheels. THOSE must have been a rubber-band nightmare!!! The Model A's used rods, not cables.