There doesn't need to be a shadowy "they" for this to be true. It can be purely the result of a dynamic in the system that results due to certain feedback loops and hierarchies in the organisation of media institutions. This is essentially the thesis of Chomsky's "Manufacturing Consent" -- that the only media that gets put in front of you has been selected by a process which is emergent and not controlled by some "cabal" but nevertheless results in a form of, essentially, propaganda which supports the power structures of the system.