@shoju What I mean is that it's not a 'right' to get money for your videos uploaded to youtube. They are a company that can set the rules for what they want to put ads on.
Why is it a problem if they decide not to let you earn money for video X?
Is it a problem because money is expected? is it a problem because 'you' use a 'free' service and they set the rules? is it a problem because people would not make videos unless they get the revenue from ads?

And to answer your question "Why should their content be given away for free", that's the thing, they do  not *have* to use youtube, but they do - because they expect to get money from what they upload. They could easily fire up their own webserver and host it there ad-free, but there is not any money in that, so no one does it, they just complain about youtube, and do nothing on their own end it seems. Complain about a free service not giving them money, feels like beggars on the street complaining about not getting money.