I don't expect any monetary recuperation, you're right in that the deal was clear to begin with. Just like I don't expect a cut of ad-revenue from a forum or what-have-you.
I just don't feel it's correct to say that the contributions actually had no monetary value, they definitely did, it's just that we handed it to Stack Overflow for free in exchange for participating in the platform.
I don't think it's unreasonable to feel a little bit jaded about it either. I'm not, I didn't contribute nearly enough to feel entitled to squat. But I get it.