Stock has to live in one place and not in two. A bottle sold over the counter in the morning and still listed on the site that afternoon costs a cancellation, a refund and a bad review.
A tester is merchandise that never sees an invoice. Without its own entry it disappears into shrinkage and distorts every brand's margin.
Expiry dates apply to cosmetics too. Tracking batches by date turns what would be a March write-off into a January clearance that still earns money.
The brand sets the prices and polices them. Running promotions demands documented margins per supplier, on pain of losing supply.
The sample belongs to the order, not to an envelope filled by hand. Two miniatures per parcel is a rule the system applies, not a reminder.
The regular customer rebuys exactly the same thing every three months. A purchase history per customer turns a plain refill reminder into the easiest revenue of the whole quarter.