I would imagine the reason FedEx and UPS and possible other couriers don't want to get involved in shipping fakes is that they know it is only going to result in problems for them and their customers at the US borders.
Why knowingly accept goods that have a good chance of being seized by customs and then having to listen to complaints from the addressees and possibly the shippers and maybe have to fight to get their fees, which they are due, even if the goods are seized.
I would think that most legitimate carriers would like to distance themselves from illegal goods, as it can do them no good, but cause them problems instead.
These are international companies, with many stockholders (including many of their own employees) to answer to. They are not going to turn down a profitable segment of business if there were not some reasons based on facts. It's not like they have someone flipping a coin off in a corner somewhere. They know that these products will not be profitable for them.
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