About once a month I run into this pattern: how easily something can be measured contributes significantly to its use and perceived worth as a metric.
The most clear example is body weight. People continue to rely on this essentially trivial metric for one reason: it is easy to measure. They associate incredibly important and life-impacting qualities (how healthy am I? how do I feel? how do I look? what can I do?) with the results of a weigh-in, when in reality weight is far too general of a measure to really mean anything. Caring about your weight is like caring about your shadow--sure, it is something that exists, and we can all look at our own pretty easily, but, like, who cares?
To prove this point on the other end of things, far more insightful metrics, like body fat, waist:height ratio, functional strength tests, and physiological tests (cardio-pulmonary, blood chemistry, hormone profile, etc) are just too damn hard for healthcare--or us, for that matter--to care about. And because they're hard, we value them less, even though they are way more valuable than a body weight measurement.
Similar stupefying patterns arise all over the place: sports, business, and economics. Tomorrow I try to connect it to credit (due to my current listening to this super cool book called Debt, by David Graeber)...don't laugh, Mr. Westbrook.