Because a posted parcel is marked delivered after 7 days if nobody confirms it. You are notified when it happens.
It is a bookkeeping step, not a claim that the parcel reached you.
Why it exists
Without it, an order sits open for ever whenever a buyer forgets to tap confirm — which is most of the time, because people confirm receipt by using the thing, not by opening an app.
The seller's money cannot settle while the order is open, so a forgotten confirmation would mean a store waiting indefinitely for a parcel that arrived on Tuesday.
What it does
It closes the order and starts the settlement hold, after which the seller's earnings become withdrawable. What is my balance?
What it does not do
It does not mean the parcel arrived. Nothing checked. If it did not come, the status is simply wrong.
It does not end your protection. This is the important part. An item that never arrived, or arrived damaged or not as described, is still yours to raise — the status being delivered does not close that door.
It does not shorten the return window for a faulty item, which is 7 days whatever a store's policy says.
If it says delivered and nothing came
Raise it from the order. Say it has not arrived and when it was marked.
Check the obvious first, because it is often the answer: neighbours, security, the gate, anyone else at the address. My parcel has not arrived
Do not wait out of politeness. The sooner it is raised, the easier it is for the store to put a courier claim in.
The better habit
Confirm when it arrives. It takes a second and it does three useful things: it ends any ambiguity, it releases the seller's money a week sooner, and it is the moment you are most likely to actually look at the item — which is when a problem is easiest to raise.
For a small store, a week of waiting on every order is real cash flow.
For sellers
The automatic mark is not a verdict in your favour. A buyer can still raise a dispute afterwards, and "it was marked delivered" is not evidence in it. Tracking is. How refunds work
More: my parcel has not arrived, how refunds work, what is my balance.