Because nobody knows how to measure these things. If they do know, they will work with a majority of people who don't. Even if they surmount that obstacle, then

Because nobody knows how to measure these things. If they do know, they will work with a majority of people who don't. Even if they surmount that obstacle, then something will go wrong and it'll be a failed experiment. And worse even yet, if you are shown to be more productive, then you've incentivized all the others on your team to gently sabotage you. That sounds more paranoid than it really is. But I've had people say bluntly "we don't want to get this done too quickly because it'll wreck the project management calibration." This is harder than it looks.