And similarly, I'd pay good money to have certain StackOverflow questions answered. But if these things seem like a no-brainer, there's a good reason why they're not available. (Third-parties have stepped in, but they're not officially supported.) Introducing money into the ecosystem can spoil people's motivation to do anything for free.

This was one of the lessons from Google Answers, an early version of Stack, Quora, etc, which paid people.

There's a good basis in psychology for this. If you look at studies about intrinsic and extrinsic motivation, you find payments (and external rewards generally) can be counter-productive and make people less motivated than if they're doing the same task for free.