Really? You think ANYONE would do ANYTHING if they didn't have to? Only a handful of people would, and even they would not be nearly as productive as if they had to. People will just think, "I'll sit in bed and play video games all day long, but that's okay, because someone else will do the hard work." Problem is, everybody will think that. Tragedy of the commons.
You can say what you like now, but deep down, everyone is in it for him or herself.
Jakob, Jakob... you're projecting (and honestly, knowing that draws us a somewhat disturbing picture of you). You need to look beyond the idea of mentally modelling other people based on yourself.
Let's talk established psychology instead. There's external motivation and then there's internal motivation. Studies have proven that people can be motivated to do work for free even when they can't be motivated to do that very same work for less money than they feel the work is worth. You don't realize that your view of human psychology utterly fails at explaining why Wikipedia exists? Studies have also proven that external motivation hampers performance in creative tasks - in other words: if you're working on a task that requires you to be creative, you'll do a comparatively *worse* job if you're getting payed for it. This is a strong argument against capitalism in the future, since it is limiting our potential for creativity.
Being asked to buy something is now considered brainwashing. That damn street grocer, I should have him beaten up for asking me to buy his fruit. My friend too, he asked me to buy a chocolate bar at the corner store, little did I know he was brainwashing me and now I need to kill him. Damn Capitalism. You have to watch out for brainwashers everywhere.
Ever bought an iPhone? A good percentage of what you're paying for in that price are the commercials for it.