I think a better answer is “maximum traceability.” A model number, common to many product samples, can serve well enough to trace where & when a product was made. This is used for food items; AFAIK, most food items don’t have a serial number for each package but a “model or batch number” that is sufficient to trace the source if needed.
It’s more processing to stamp a unique serial number on every single manufactured item compared to a batch number on thousands at once, so why do it if it serves little useful purpose?