It's not responsible for it but I can almost guarantee you the reason is because it wants to save itself the headache. Meaning, it would rather just reject shoes that have obvious defects/bad craftsmanship than sell them through and then have the buyers of those shoes emailing and calling to complain and demanding refunds and/or discounts as a result of receiving crappy pairs. If I ran SX, I'd do the same thing. The more complaints and disputes you receive, the more man power you require to deal with all the cases. It's not worth it and way easier to just reject blatantly bad product.