Same reason you use jack stands instead of just a jack: Because fluid leaks past the seals in the piston causing the braking force to reduce... Parking brakes have to be able to hold their clamping force indefinitely.I feel dumb for asking this, but I will anyways...
Why don't car manufacturers integrate the e-brake system into the rear brakes themselves? Wouldn't it be more cost effective to have rear brakes that do both stopping and e-braking?
Someone explain this to me. Is it because of ABS or hydraulic systems?