When technological progress allows for greater weight efficiency, authorities prefer higher performance (at the old high weight) over keeping the performance and cutting the weight.
This is just another example:
By Matthew Cox, military.com
The virtues of frugality and modesty could help us with many problems and save us many wasteful expenses, but they are also against bureaucratic instincts.
This means there's an opportunity for being superior to your adversary; break free off bureaucratic instincts like these, and pursue neglected approaches and virtues - such as modesty and frugality.
Another classic example is development of high technology big ticket items (say, fighter jets). The costs explode for every per cent performance engineers squeeze out of the design. A 90% performance solution can easily cost less than half of a 95% performance solution and a 100% performance solution may be technologically impossible (unless you extend the program for a decade or two).
Still, the frugal and modest enough 90% solution is terribly unpopular. This phenomenon worsened since military procurement became so very much broken that big ticket items have become all-or-nothing affairs. The British and French were still able to go for a 90%, frugal SEPECAT Jaguar attack aircraft design when it was merely one of several modern combat aircraft types in their inventories. This didn't work so well with the Typhoon and Rafale any more, and today's F-35 is basically a 100% solution in some regards (avionics) while irritatingly being a 80% solution in others (flying).
Frugality and modesty can only help us if there's a stern and decisive, competent and benevolent oversight over the bureaucracy. And it's only possible to stay frugal and modest with a lot of self-discipline.
Both good oversight and good self-discipline are in very short supply in Western defence establishments.