Brick and mortar store here. I used it daily. It allows you to send an invoice to a customer to pay online (say a deposit for a special order). If you don’t have it reserved or in stock they can’t finish the transaction.
If you are getting customers to put a deposit on an item that you want to be able to edit properly once they have paid, you can reserve the item so it’s not appearing in your store. Then you can still track inventory and items associated with orders and won’t be clumsily adding stock in and out.
Particularly good for draft orders as Laybys.
Are you ok btw? Seem very vitriolic about reserveing items xD