Saddles with springs are particularly good for bikes that have you in a more upright position. (that's one reason you see them on a lot of older bikes)
Sitting upright puts most of your weight straight down your spine onto your sitbones. Every bump in your ride will have your weight coming right down on your seat, not on your legs or hands. Springs help absorb the shocks on both your spine and your butt.

On a less upright position road bike, your weight gets more distributed between your seat, legs, and hands, and your spine is more horizontal and can flex with the bumps. More of your weight is on your legs as you ride (if you are well balanced that is). There is less weight jamming down your spine onto your seat with every ride bump. Thus, springs are not as needed.

FWIW, my road bike is sort of halfway between a racing position and an upright position. Speaking for myself, I don't feel any need for springs at all even on long rides. When I do hit bumps unexpectedly, I can actually feel my non-sprung B68 under-saddle frame rails flex down and back up with the impact.