Rubbish click-throughs and shitty impressions, these are the real reasons a sensible company enters into an affiliate agreement. They are feed up with paying for traffic that doesn’t convert.
But affiliate marketing is results based. A publisher might put a banner on their site for booking.com. Someone reads an article about running with the bulls in Spain, gets inspired, clicks the link, and sinks a few thousand into a holiday.
It doesn’t matter if a million people saw the ad, clicked the link and spent ten minutes thinking about booking, the advertiser isn’t paid until that customer checks out of their hotel.