To illustrate my point.
Last year Transport increased the standard passenger weights. This reduced the effective passenger load of each aircraft by approximately 10%. On the surface, more accurate pax weights is a valid improvement. But what is an airline to do- block off 10% of formerly available seating? Not likely. Shortly after this, a company memo informed us that our fuel burn numbers had been revisited, and had been updated to "more accurately" reflect the book values. Our standard alternate fuel was therefore reduced by 17%. Net system safety benefit= zero.