There are various types of employee pay arrangements other than hourly and salary that do this (even though, some salaried jobs do work the way you describe), like piece work.
And it's already really common for non-employee contract work to function that way. The guy who mows my lawn gets paid the same amount no matter what speed he mows it.
That being said, there are plenty of salaried jobs where people are assigned measurable responsibilities to attend to and don't have assigned work hours.
https://en.wikipedia.org/wiki/Piece_work
And it's already really common for non-employee contract work to function that way. The guy who mows my lawn gets paid the same amount no matter what speed he mows it.
That being said, there are plenty of salaried jobs where people are assigned measurable responsibilities to attend to and don't have assigned work hours.