Comment by B-Con

People want to do X, so the metric is how much X can be done.

Everyone is over-complicating the explanation. The answer for "why are we fixating on this bad metric" is almost always the same pattern.

Broad audiences need simple metrics to talk about. If the metric itself requires nuance, it's hard to communicate and hard to reason about. It's easier to push the need for nuance from understanding the metric itself down the road to where the metric is applied, which allows everyone to ignore it in immediate conversation.