Reinforcing what Shotgun 693 said, there was some elitism in the FBI ranks. Regrettably, in the area of gambling, narcotics, organized crime, and prostitution, there were a very small percentage of police officers, primarily with the larger departments, who had allowed easy money to corrupt them (see the Knapp Commission Reports). Thus, on many operations, you could not coordinate with the local police force unless you enjoyed raiding vacant sites. To be sure, the corruption occasionally extended into federal ranks. It doesn't mean the feds were cleaner than the locals, it means the locals were closer to the action and more streetwise. As a result, a level of animosity sometimes existed between federal and local law enforcement because the locals expected to be notified of an operation in their own back yard. Also, the FBI had a reputation for not sharing investigative finding with other agencies. You'll recall that this lack of agency cooperation prevented us from connecting the dots regarding 9/11.
Before anyone breaks out his flame thrower, remember, I said a very small percentage, not all of them.