Whew this is going to be a long answer...
First thing that needs to be understood about DHGate, World Wide Brands, AliBaba, etc...
Nobody spends money to manufacture things, then sits them on a shelf and hope they sell. For this reason, if you ask any manufacturer that says they have the inventory of whatever kind to take a picture of themselves holding up a sign that says "Bobo" next to the inventory, they will have a million excuses as to why they can't. What we call "dropshipping," they call "normal selling" - often, people sell stuff in huge quantities and then hit the streets with customers money buying stuff from street vendors or on sites less accessed by non-Chinese such as TaoBao. Essentially, 95% of the people on all of those "B2B sites" are middlemen looking for an extra cut. Living in China, I can feel free to say this... but theres a good chance you are being fucked over and not even realizing it. In China, its better to make a quick dollar and not worry about long term business.
This is also how people overseas(Asia) protect themselves. If you buy, say 200 fake bags from someone on DHGate and they ever get into trouble which is really starting to happen now a days, they will tell everyone "This customer said they were the company that were allowed to have these manufactured, we didn't know, they lied to us!" and will totally write up complex fake e-mails. This is how major exporters of fake goods get into a little more trouble. But seriously, its rumored that big busts of fake goods is well reward to authorities in China. Only a rumor, I can't confirm it, but the fact that people are really going after suppliers of fake stuff is not false.
Shipping agencies HATE replica stuff way more than they did 2 years ago. At the same time, they also try really hard to save face. A shipping agencies will agree to ship 40 KG of Nikes, well knowing they won't really send them out, it will sit in their back room and they will sell it all within China and then claim it got picked up and destroyed by customs. If they do ship it out, they will have to forfeit their entire business and profit if caught. Do people in China get in trouble for sending replica stuff out? Yep. Do people that live in another country get in trouble for buying replica stuff? Yep. Can you claim you didn't know the items were fake? Nope.
The reason why you probably can't find anything on those sites is because American contractors can send notices threatening that everything with the word "Nike" be removed from the site or they can be sued by Nike, and the rest of the "big brands" - some people will say its because America technically owns the internet, but I won't comment on that. This is unethical in my opinion, to assume everything is replica but more-so to stop people from buying items second hand to force them to shop in the high end stores and pay full retail prices. I feel this shits on consumer protection laws.