Business as the middle man

I am planning to start a business of being basically the middle man of some products.



For example, I could act as the middle man between some products manufacturers in China, and then bring it over to North America to some retail stores.



They could be food, drinks, general products. etc.



My question is, what is preventing these retailers in North America from contacting the suppliers in China directly. Thus eliminating the middleman, Me in this case.



I mean, I could see how the retailers can just go. "hey this is a good product, Im ganna contact the suppliers in China directly and cut the cost for having to pay this middleman"



Thanks in Advance guys