I always find this to be a funny point in these conversations. The entire discipline of "agile development" exists because it's so hard to have foresight into the requirements of a software product up-front. By extension, I don't see how we think it's possible to define expectations for employees up-front and then pay them only based on results. If you look at agencies within our industry, for instance, about 0% of them will work on fixed-price contracts - it's always time-and-materials. Knowing what we know about software development, I don't see how individual employment can fundamentally be any different...
https://dilbert.com/strip/1995-11-13