Those are companies that derive value from advertising. Steem is the equivalent of the upvote on those platforms, which has no value, even though there are billions of users. You seem to be missing that important point. What good are users if the currency has little to no value? Content sites already exist without a currency and they do a much better job at rewarding "quality". In order for the currency to have value it has to appeal to investors, which it doesn't. If you could somehow tie the advertising revenue to back the currency, then you might have something, which is exactly what Voice is going to do, but apart from that you need to appeal to investors if you want the currency to have value.