I have tried this too, not recently though.
As gooner pointed out it’s the tracking.
The customer needs to buy immediately or you get nothing, and they may go back to Amazon and buy thousands of $ worth of items in the next month and you get zilch.
You can make little sites and leave them to fend for themselves and consider what little they bring extra pocket change, or you can add books to your site as customer service. But as a serious source of income it’s useless.
If you have good volume traffic for a big ticket item, such as appliances or furniture, you might make some decent money by affiliating with Amazon.