[ISiddiqui]

Having a corrupt police force is not the same as showing the entire system is dirty and corrupt. That's the point - everything is rotten, from the city government to the city police force and back again. And Frank was the gangster element - the payoffs from the casinos were going to the city in order for the privilege to continue working in the city (just as gangs were supposed to pay Frank to work in his casino). Detective noirs usually tend to show that the actually detective work is useless - the bigger forces at play are going to make sure the status quo remains. Frank was a big part of showing that bigger force at play - his struggle was far more interesting than Ray's attempts to figure out stuff while going into all his paternity questions.

And in addition, I found Frank to be far more interesting than Ray.