system
Given the following post, respond as if you're commenting on Reddit:
human
why aren't the top 'economists' billionaires?

I apologize if this post shows my ignorance; I have no formal academic economics experience. 

It seems to me that people who are at the forefront of modern economic theory would be suited to run businesses.  Why do they not position themselves to be CEO's or COO's of big businesses?  I'm sure that academic institutions pay them a comfortable salary, but when I hear about these top-tier economic theorists, I always wonder why they aren't in a mansion in paradise somewhere.

i realize that this question makes many assumptions and generalizations, and very well may not be a valid question at all.  But, can anyone offer an answer to this?
gpt
An economist and a CEO are walking along and see a $20 bill on the ground. The CEO says "Hey, $20! You should pick that up!" 

The economist replies "If that was really $20, someone would have picked it up already."