One can make thinner tubes out of modern steel but at a cost in rigidity. What steel tubing makers and modern frame builders probably woul d prefer you didn't know is that the single most critical property of steel a s it relates to ride, it's elastic modulus, is essentially the same for fifty year old tubing and the latest super wonder pipe.
Pretty similar story comparing modern "super" Al alloy and sixty plus year old RR Al alloys developed for Merlin airplane engines. Not a whole lot of difference. The low hanging fruit were picked decades ago.
Kurt Sperry
Bellingham WA