Why Does the Sharing Economy Overlook Brainpower?

No, I have a well-paying job, so I don't need to spend my leisure time earning small amounts of money. Activities like learning new skills would give me a far better return on my time. However, I might be willing to exchange my thoughts for large amounts of money (consulting at the market rate).

There has always been a "sharing economy" for brainpower - it's called freelancing.