I'm not sure all this weight talk is the relevant benchmark for steel over the past 20 or 30 years. Lightweight steel has been around a long time, so the focus on development was, primarily, not to make tubesets lighter, but stiffer at the same weights. I think the physical properties of steel kind of constrain the weight issue due to practical durability and construction issues, anyway.

I'd be willing to bet that a current 19lb steel bike is stiffer than a 19lb bike of the '80s or even '90s. That's been my experience, I think (Bridgestone RB2 vs Breezer Venturi); I don't recall actually weighing the RB, though. It was whippy, and I weighed about 20lbs or so less back then.