In the case of cost per mille/click, the publisher is not concerned about whether a visitor is a member of the audience that the advertiser tries to attract and is able to convert, because at this point the publisher has already earned his commission. This leaves the greater, and, in case of cost per mille, the full risk and loss (if the visitor cannot be converted) to the advertiser.
Aim for quality over quantity. Having a vast network of affiliates will not necessarily help you earn more money. According to some experts, the key to successful affiliate marketing is to find the right affiliates that will drive the most results for your platform. Those affiliates may be big sites, small sites, or a combination of the two, but the most important thing is to build and maintain strong relationships with your chosen affiliates.