It's not so useless. It's one exercise in why broad indices can be misleading.

Creating value in energy production is good, up to a point, and that point depends on whether you are an exporter or not. But if energy becomes a too-large part of the economy it does so at the expense of the rest of the economy.

The same can be said about health care: Health is good. So spending on health care is good. Until it exceeds what other nations pay to get the same health. Similarly, a healthy financial sector is good, unless it drifts into excessive financialization.

Illustrating how one economic sector becomes a vampire is useful because it illustrates how raw GDP can hide vampires that suck the blood out of quality of life.