It is the networking effect. Same can be said for what gives Bitcoin or even the US Dollar value. It's people accepting it and the free market process. I do think Steemit and the platforms that are and can be developed on top of it can be game changing. I disagree with your assessment as well that YouTube doesn't make money on Content because it drives the advertising. Much like T.V. and the Super Bowl which gets crazy prices for advertising. Content drives advertising $$$.