How do some people get away with sending fake Louis Vuitton bags to the US from China, and others don't?

I was wondering how is it that some people will send a fake louis vuitton from china, and get away with it, and others send the same thing, and it gets into the hands of US Customs?|||Customs right now, is a bit messy. They do random checks and there are way too many travelers passing in and out of the US everyday for them to check everyone. Furthermore, sometimes they transport them in lesser amounts at a time. The more you have, the more likely you are to be caught.