I like your analogy; but of course, there comes a point where reducing weight in an automobile does have downsides: it might be more noisy because of reduced sound deadening, less safe because of removal of crash structures, less waterproof because of removed seals, and so on.

The point being, in both cases, the virtue lies in finding the optimal balance: maximising the benefits of frugality without going too far and falling down the other side of the curve.