Because politicians dont think they are getting a large enough piece of the pie. Same as it ever was.This shouldn't be viewed as Apple doing anything good or bad. If Apple wouldn't be here, another public company would gladly take their place.
This should be viewed a problem that a $3 trillion market cap company will eventually face. There's no good proxy for this size; not even standard oil. When a company grows this large, and is this successful, with such market concentration in so many segments, there will eventually be some antitrust action.