People with sickle cell do. That's part of why certain genetic defects are prevalent in certain populations: survival of the fittest in circumstances where the alternative is worse.

I think they have signed "right to try" into law. But there are very good reasons we want to test stuff before taking a big step. People tend to die as our way of finding out the theory is only half baked.

That's how we got rounded airplane windows: by planes going down in gruesome crashes that killed everyone on board, thereby serving as a clue that there was a design flaw somewhere in our lovely new jets.