The stock list says the part is in bin A-127, but it was moved during a reorganization and nobody updated the record. Now someone walks the aisles looking for it while an order waits.
Location records drift because updating them is extra work. Writing down bin and item numbers during a busy put-away, then typing them into the system later, is exactly the step that gets skipped.
If recording the move takes no longer than making it, the record stays current. A barcode on each bin and on each item makes that possible with a phone.