As an adult living in a world with other adults, if I want to get paid for my work, then I'm going to setup that interaction ahead of time.
If I wanted to con people, then maybe I would put something of value out for anyone to take. Then once people take it, I would pressure them for something of value in return.
If I give out a gift and it makes someone want to give me a gift in return, then that's nice. But they aren't required to give me a gift. That's the whole point of giving a gift in the first place. It doesn't setup a compulsory need to reciprocate.
When I release OSS code, I expect everyone to be able to use it, and I do it on my own schedule, based on my own interests. It's purely self-motivated.
Were I to write code for your company, I bet you wouldn't let me release the code to anyone else (I can see it in your little eyes) and you'd definitely demand to control what I write and how quickly. It's externally motivated. The external motivation I choose is money.
It's a traditional economic model in the arts. Most musicians and photographers put shelter over their heads and fill their bellies with nothing but "exposure".
