What Amazon really nailed, and the reason I buy like 90% of things from them, is the easy and known shipping and return policy.
But the second reason I buy from Amazon is laziness. I am too lazy to look up the (often confusing) product on their company store, I'd rather just buy that product through amazon. To compound my laziness, I don't like having to once again fill out my email, home address, and credit card for the thousandth time when I go to their site.
But if I don't have to find and navigate to their site and I don't have to fill in my information for the thousandth time. Now, we are talking about me realistically considering a direct purchase.
This is likely good for the consumer, and largely good for the world (less centralization).