I do agree, that mafia act as a government. But there is still quite a difference to a democratic government. It is more a olygarchy/despotism.
But I believe our roots of government back in the middle ages, when feudals conquered new peasants to profit from them, were very alike. And there might be still characteristics in our institutions from that legacy. People definitely view it that way, when they pay taxes ...
Note that I don't believe this myself - I'm on the "Taxes are the price we pay for civilization" side of the argument but I can see that those on the other side have a stateable case. My main objection is that I've never seen any plausible description of an advanced civil society that doesn't rely on compulsion to pay for things.
Eric Hobsbawm wrote Bandits, a nice little volume on organized crime. It's written from a different political angle.
Also some people really, and reasonably, argue that government is nothing else but a kind of Mafia that simply one the competition for being called "government". You also know the discussions of "freedom fighter" versus "terrorist" declaration, right?