From my point of view, you, and customers asking for refunds after their hardware has been manufactured in general, are a liability. When manufacturing something you need to part with your money months before having hardware in hand. You most likely will try to part with only as much money as it is going to end up making you money, so you will use customer preorders to gauge how many units need to be in the batch. A customer asking for a refund after the order is sent to the CM and before it is delivered creates a cashflow problem. It's easy to see how that problem could become very critical if you don't have deep pockets and if you can't swiftly resell the cancelled units.