Recently when visiting the cellerman of one of my favorite North Texas craft breweries the production manager was wandering around the brewhouse clearly counting things. The cellerman asked "Didn't you just inventory everything the other day?" The answer as an unsurprising, "Yes, but I am not sure which spreadsheet has the most recent data."
And the beat goes on.
Not only are spreadsheets unreliable insofar as they are not validated for accuracy, but they are usually also uncontrolled. It is, of course, possible to validate a spreadsheet's computations and control access and updates on it. But nobody does that.