Usually, the springs do not increase in spring rate enough through to make up for the reduced ride height. That is, they do get stiffer, but not stiff enough.
Ride quality is also very subjective. My C10 came with heavy rear leafs, and stock 1/2-ton coils. I found the ride to be imbalanced - too stiff in the back. Many folks put 1-ton coils in the front when they lower them to make them adequately stiffer, but others complain about the ride being way too harsh. I switched to 1-ton coils up front, and while yes it's stiffer, I've already forgotten about them because in my subjective world, they are not excessively so.