I suspect the hidden factor is population growth. You can find numerous examples of things that become less efficient (more difficult/costly yet also crappier) when more people are out there demanding that service. Or not even using the same service, but simply interfering with each other in ways unrelated - getting in each other's way, affecting each other. Cost is not in a linear relationship with population size, or maybe it's population density. There's a kind of friction that increases. Diminishing returns of scale & complexity, you could call it.