Why do Inventory systems allow dispatching quantities that are greater than existed?

[Eslam Elbyaly]

Hi,
I can see there are many inventory systems if not all allow dispatching quantity of products when the warehouse does not have sufficient quantity.
For example, I could sell 5 units of product A when the system says there is only 2 units in the warehouse. It just displays a warning that that transaction could cause my inventory to be inconsistent! Why does it allow that if it can cause harm? Is there a use case when one would need such feature?

[Steve R Jones]

I would assume there is a "permissions" type of setting to allow the inventory to go negative.

I would also assume it would update a "back order" list automatically.

Once the inventory is restocked, either a reminder should be produced or automatically create a need to ship items list would be created.