Lets take the example of Reddit. Reddit could have kept its costs to the minimum and could have run the site with the ad revenue that came in. In fact they could have talked transparently about their opex and asked for a simple donation drive every now and then like Wikipedia. If need be, they could have removed silly GIF replies and other stuff and focused on text alone. However this would not let them become the next Facebook. That’s what they wanted to be. At some point in their story was a choice to be forums 2.0 or get into a race to become a cash grab. Sadly they went for the latter.