Pay for performance is a perfectly valid way to solve these problem if the outcomes are clearly attributable for the service provided, but consider cases like strategy consulting where the outcome of hiring a strategy consultant is hard to attribute.

One of the things I was interested about is problems where there is possible deniability and attribution ambiguity, in these cases my thinking was it is better to scope and anchor to a larger issue that might occur and align incentive towards a more holistic outcome rather than specific service. The futures approach was a general way of doing it which is agnostic of the problem in hand (though the specific implementation of it would inevitably be tied to the outcome you want in the end).

The doctor example is a common example I keep using since it is very simple to explain, it is purely for exploratory purposes and I did note that it is quite possible not all doctors and consultants might do this. My point was not to deride anyone but rather to just explore an idea.