Ads allows for much wider distribution of content and much lower per-user costs. If you had to pay to access the content the number of people who can pay is nec

Ads allows for much wider distribution of content and much lower per-user costs. If you had to pay to access the content the number of people who can pay is necessarily much smaller and so those people would have to pay more per person than the ads make per person. If you want to rely on donations, well, you won't find enough people to donate to support the amount of content we have today.