The basic answer to your question is that it takes a lot of energy time and passion to make internet content and a sane person would want some sort of return for that investment. Why on earth would creative people pour hours of thier lives into giving the masses of passive (not unlike the leech) internet content consumers a free ride.
Interesting. Sounds a bit like the job description for a position as a moderator :lol
I think it´s the same drive that lets people start work on short movies. To get things going, to make something for their portfolio. Or simply to have a vent for their creative energies?