Not all scientists are flakes. Not all politicians are dishonest pieces of shit.
Or are you going to deny that SOME scientists who are interested in maintaining a status quo? Zahi Hawass is a prime example.
http://en.wikipedia.org/wiki/Zahi_Hawass . He has a reputation for saying whatever needs to be said in order to maintain the facade of "accepted" Egyptian history.
Anyways, to answer the question, simply because if humanity knew the truth about existence and the nature of reality, our "jobs", our "families", our "possessions", our "lives" would be meaningless. I believe the human mind is capable of much more than we consider now. I believe ESP, telekinesis and other mental powers can be learnt as they are inherent abilities in humans, just as breathing or locomotion is. Humans would never settle for 9-5 jobs, would never settle for living the existence we do, if we could reach for anything better.