This generates a lot of false positives too - if I have bought something and I see an ad about it, I may still click at it out of curiosity but without any intention to purchase it. (And rarely has an online ad or copy induced me to purchase something again that I just bought). So Ad networks do have an incentive to keep showing me ads that I have clicked, whether it would convert into sales or not, because they make money from these clicks. I think that's why "personalisation" matter to the online ad industry - not because it increases conversion and makes more money for the advertisers, but because it does increase revenue for the advertisement platform.