It's important to distinguish between inadequate intake and suboptimal intake. I'd wager the medical establishment only refers to the former as hypokalemia.

Yes. It could also be that the potassium and sodium concentrations don't vary much no matter what your consumption, but your kidneys have to work harder to maintain the balance which could have health effects. I don't see much hypernatremia either although sodium is way overconsumed. I think this is because water follows sodium and therefore as you retain sodium you retain water in the extracellular volume. Therefore the measurable concentrations don't change although you have excess sodium in your system. I think potassium and water don't interact the same way because potassium is mostly intracellular and cells can't stretch arbitrarily whereass the extracellular volumes can.

Optimal potassium intake probably varies hugely depending on your sodium intake since they interact inseparably in the human body.