It's at odds with "heritable or not", the interesting question to us peasants. If there's a disease that gives you spots, we want to know if you can get it from your ma and pa. We don't want to know that nearly everybody hides the spots with makeup.

Then there's the matter of whether there's just a small population with the genes for it, and whether it's polygenic, or mitochondrial, or otherwise non-mendelian, and all that gets factored into this heritability value along with cultural things like the use of concealer and the probability of having your face torn off by a bear. It kind of reminds me of inflation, as a useful measure.