How so? It costs money to store & retrieve this content, at reddit scale (100m active monthly?). Ads clearly weren't paying enough of the bills, so what's the next best option?
Reddit made $500M in revenue last year, yet is unprofitable. The reason isn't its AWS bill, but the "must 5x every year no matter what" mentality of their VCs who are looking for their exit. This pushes companies to overhire, add useless features and waste money on user acquisition just to chase that growth chart and have a successful IPO roadshow.