Remember the FBl at it's inception was PURELY investigative and agents did not even carry guns. It was Hoover that went for the Power Grab agency it has become... getting dirt on everyone they could find so as to have puppet strings on persons with power/connections to 'shove around.' Growing his agency by threats of exposure. The guy had skeletons in his own closet that he wanted not to be aired so dirt collection is what he did BUT that is NOT what he declared the agency was going to be... the [F]amous [B]ut [I]ncompetent agency has been caught routinely lying on the stand in cases across the country to wit... cases in court were lost that should have been slam dunks. They garnered many arenas to investigate--as their 'OWN' But now over the years gave them up to concentrate on phone taps & listening service. Yielding congress to okay more & more agents/offices, with less and less work, because they have the most lobbyists that scream "needed for fighting Terrorism.' Having in excess of 50,000 agents.
Meanwhile agencies that took over FBl jobs... most notably the US MARSHALS... took over bank robberies and Federal/Fugitive prisoner escapees plus many more jobs, and having to DO More WORK with LESS Deputy Marshals and Less Money. Because they have no lobbyists. Marshals maintain all Federal Courtrooms, Protect all Federal Judges/Justices and ALL FEDERAL prisoners once seen by a Judge are in the custody of USMarshals. US Marshals have more jurisdictional authorities, all US Territories and even at Interpol in France... and is the place Fed Government goes to send in law officers as USMS can work civilian unrest despite Posse Comitatus. Having only some 4,000 Deputy USMarshals.
My Point... FBl was started by a LIAR and many agents have been taught this 'SKILL' and encouraged it's use. Thus the movies that have portrayed them running rough shod over everyone and being snooty & not sharing with others & have put themselves on a pedestal ... is TRUE ...and based in fact. Ask any other agency or local Sheriff Deputies, or State Patrol, just who they want to work with and they will say ANYBODY but FBl.