I actually think it's also due to the immaturity of the field and the rate of change for the technologies / practices within it. We seem to be in the only field

I actually think it's also due to the immaturity of the field and the rate of change for the technologies / practices within it. We seem to be in the only field where a freshly minted PMP can get a job even if they have no real experience. Why else would we have so many people who have never written an LOC managing developers? Engineers generally don't. Job security and employee loyalty is also at an all-time low so make sure you're billing enough to cover your retirement.