If I was being paid for my outcomes I would manage my time entirely differently and would find ways of being more productive than I already am so that I could work less hours. I think this is a hard pill for people's bosses to swallow, that their employees do have the capacity to be more productive but they won't because we're being paid to be at work and so incentives are not aligned.

My boss is very happy with my productivity and I am very productive. I don't think he could conceive of me being any more productive. But I know that if I could arrange my own days and hours I would be more productive. But this would be inconvenient to him and so he would likely rather have me predictably available than fully optimised. Which is an understandable tradeoff if frustrating from a personal perspective as you feel as though you're wasting time. It's just that your wasted time is actually valuable to someone and that's hard to grasp intuitively.