Well, to start, it's not a place that people wake up in the morning and visit hoping they'll be drenched in video pre-roll ads. For that, we have Wikia. ;)

EDIT: I noticed that the article kindly compares reddit to Wikipedia, which Wikia is basically the for-profit sister of, in fact originally created by hosting content that was removed from Wikipedia and putting Google Ads on it. Both Reddit and Wikia have the problem of generating revenue from the people who create the content that the revenue is generated by, many of whom are children.