I take your point, but I personally think that it's not that necessary to hedge and it's safe to say that most people (in developed western nations) don't need to shower every day. Very few people are working demanding physical jobs in which they get especially dirty/sweaty every day. And, given the obesity crisis in the west, I doubt that many people are working out every day either.

The real answer is that people need to shower enough so that they A) feel comfortable and B) don't cause issues for the people around them. A is a bit fuzzy, and will change depending on what an individual is used to, but most people in most situations won't run into B if they are showering every other day (or even every 3 days) modulo things like "I went for a run this afternoon" or "I worked in the garden all day" etc.

The edge cases are probably rare enough to say "you don't need to shower every day, but if you get particularly dirty/sweaty, then you should shower" and you will be correct for most people. The few people who do need it every day can probably work it out for themselves.

Perhaps the largest exception to this is teenage boys who just really are a biological marvel of smell generation. They should potentially be showering multiple times a day for the sake of those around them.