One thing every company has to deal with is the small number of people who want to rip the company off. From the employee slipping a few bills from the till to the customer who tries to get a refund on the torn and stained wedding dress, there is a tiny minority who will lie or cheat to get something they don't legitimately deserve.
So every company has processes and policies to keep dishonest customers from taking advantage of it. You can think of this as an organizational immune system: identifying the potentially harmful customers and transactions and stopping them in their tracks.
There is a cost to this. In addition to the direct costs of implementing systems, training, and policies, there is the problem that no system will ever be perfect. There will always be someone who find a way around the system, and there will always be the unlucky customer who really did get three defective products in a row and doesn't appreciate being treated like a thief.
It's hard to strike the right balance between a strict set of rules--which will frustrate legitimate customers with real problems--and a more permissive attitude which would benefit the bad guys.
I see a lot of companies which are far more worried about the slight chance a customer might get somthing they don't deserve than the chance a customer might go away annoyed or frustrated. For example, if a customer calls to complain about a $1 billing error, it costs far more to spend any time investigating the mistake than it does to just give the customer the buck. But try calling your phone company or credit card company to compain about a $1 mistake and see how much time they spend making sure you really deserve that dollar.
If the systems to prevent beign ripped off are like a corporate immune system, then irrationally strict policies are like an auto-immune disorder. It's the corporate immune system mistakenly assuming that legitimate customers are bad guys and attacking the wrong problems.
Treating customers as the enemy is no way to win long-term loyalty.