A properly built steel frame is more shock absorbing than an aluminum frame. Don't confuse the cheap steel bikes being sold with a quality frame from Colnago, for example. For me the issue was the change in frame geometry to accommodate freewheels and cassettes with more than 5 speeds. Mass production moved to aluminum and carbon fiber for the mid to high level bikes.
That is changing though with the current situation where Trek adds $1200 to the price for a bike with a carbon fiber frame over the same bike with an aluminum frame.