It’s not a racket — the state does use its monopoly on violence to enforce your title to the land. Otherwise it would only be yours until someone bigger and stronger came by.
And the mob really does honor their protection racket, too. If some punk comes and tries messing with a store protected by the mob, the mob deals with the problem.
Yet nobody goes around looking to purchase protection from the mob either, do they? The key problem with the arrangement isn't that the protection isn't provisioned, it's that the entire arrangement is involuntary and forced upon the business owner through threat of violence, whether by the mob or the state.