Wait, what? SE doesn't want people to give them money?
Even following what you're saying, you have to consider this. If SE, today, were to start charging a monthly subscription fee, there would be some people that would pay it and continue playing. Yes, it's safe to say a lot (probably most) would not, but there are some people that are willing to pay for this on a regular basis.
Logic would then dictate that more people playing would mean more subscriptions. Any way you look at it, it's in SE's best interest to distribute the game as much as possible.