There are three main contributing factors: - Users are not the customers, so there's little point in optimizing for their experience, except to the extent that

There are three main contributing factors: - Users are not the customers, so there's little point in optimizing for their experience, except to the extent that it impacts the number of users your customers reach with ads. - Users do not favor faster websites, so as long as you meat a minimum performance bar so they don't leave before the ads load, there's little to gain from optimizing the speed. - For users that do care about load-time, it's hard to know before visiting a page whether it's fast or not, and by that point the publisher has already been paid to show you the ads. A helpful solution would be to show the load time as a hover-over above links, so that you can decide not to visit pages with long load times.