Why is Value so Difficult to Measure in Project Management?

People struggle quantifying the value of project management. Partly because people value the outcome not the process. When you go to a restaurant for dinner, you care about the dinner not the process by which it was made. Part of it is also the new projects are difficult. Making dinner is a known, repeated process. Implementing a large new application in your company hasn't been done before. That makes it difficult.

Change is difficult and no matter what anyone says about their experience, they've never made changes in your company before. I believe the measure of this difficulty was described a long time ago:

"There is nothing more difficult to take in hand, more doubtful in its success, more dangerous in its execution, than to take the lead in the introduction of a new order of things. The innovator makes enemies of all those who prospered under the old order, and only lukewarm support is forthcoming from those who would prosper under the new. Their support is lukewarm partly from fear of their adversaries, who have the existing laws on their side, and partly because men are generally incredulous, never really trusting new things unless they have tested them by experience.” - Machiavelli

Its easy to forget that people have struggled making changes for a very long time. New technologies don't change that. Machiavelli wrote this in about 1515. Maybe things haven't really changed all that much in the last 500 or so years.