Dates are the real inventory problem. A supplement approaching its expiry has weeks of value left and then none, so knowing what is about to run out of time is what turns a write-off into a promotion.
Ordered-in items belong to somebody. A product brought in for one customer sits on a shelf with a name attached, and forgetting to ring them means both a lost sale and a lost customer.
Regulars buy on a cycle. The same supplement every six weeks is predictable, and a shop that notices when somebody's rhythm stops can ask why while the habit is still recoverable.
Categories are not equally profitable. Refills, chilled goods, supplements and packaged food carry very different margins and wastage, and a shop measuring only total takings cannot see which shelf is paying for the others.