Consider the measures prefixed with 'real', for example, 'real wage'. The concept of 'real wage' isn't meaningless, since it captures the relation between wage and purchasing power when inflation is involved. But what about cases where inflation is not involved, or cases where we need to consider interactions between some other factors and inflation? In those cases, the concept of 'real wage' is often impedimental and misleading, a ratio indicating purchasing power would surely be a better choice.

Consider the concept of 'equilibrium'. I can hardly see any empirical foundation of 'equilibrium' when it's invoked by empirical economics research. There are stationary periods of prices. But it's a different story to interpret such stationariness as a state of equilibrium with a mysterious process forcing prices to always gravitate to this state. This interpretation is without empirical foundation and yet its reliability is often assumed a priori in the research.

If you are not persuaded, it's okay. Regardless, I don't believe hypothesis formation is irrelevant.

EDIT: On second thought, my case against 'real wage' above was missing the key. The key is that purchasing power is what matters, and the purchasing power (most of the time local) of stock variables (e.g. savings) is what matters. To adjust flow variables by inflation is often misleading.