Not at all. The crux of the question was "Would not the quality of todays metals allow for lighter doubles with similar or better strength?"

The question is based on the premise that nitro DR weights have somehow heretofor been governed by the strength of the steels available, which isn't true. Modern fluid steels permitted making them lighter than anyone has ever wanted them 100 years ago. Weights have been governed by other factors, as Marrakai pointed out above, which make just as much sense today as they did then.

If you want to know why they haven't been built lighter, and probably won't be in the future, then the real answer to the question is "Why would you want to?"