I see where you're coming from, but this assumes good behavior and discipline which most people/teams struggle with.

If a business can get away with some margin of error being acceptable, more power to them. But if not (or doing so would cause additional problems; what I'd imagine to be true for a non-trivial number of orgs), it's wise to consider the nature of the tool a lot of people are suggesting is mandatory if you're dependent on consistent, predictable results.

That's fair. A heuristic that leaves some opportunity on the table due to org capability is a reasonable one to have.