One of the main problems in Internet marketing is that it is often a "the winner takes it all" game. That means that the best website will get the deal and all other websites will get nothing, no matter how good they are.
Suppose someone wants to buy a green widget. He searches Google, takes a look at the top 10 results and then decides to buy something on one of the sites. That means that one site gets the sale and the other sites get nothing.