From the Introduction: "'Almost every headline-grabbing prosecution has involved a conspiracy charge.' Terrorists, drug traffickers, mafia members, and corrupt corporate executives have one thing in common: most are conspirators subject to federal prosecution. Federal conspiracy laws rest on the belief that criminal schemes are equally or more reprehensible than are the substantive offenses to which they are devoted. The Supreme Court has explained that a 'collective criminal agreement--[a] partnership in crime--presents a greater potential threat to the public than individual delicts. Concerted action both increases the likelihood that the criminal object will be successfully attained and decreases the probability that the individuals involved will depart from their path of criminality.' Moreover, observed the Court, '[g]roup association for criminal purposes often, if not normally, makes possible the attainment of ends more complex than those which one criminal could accomplish. Nor is the danger of a conspiratorial group limited to the particular end toward which it has embarked.' Finally, '[c]ombination in crime makes more likely the commission of crimes unrelated to the original purpose for which the group was formed.' In sum, 'the danger which a conspiracy generates is not confined to the substantive offense which is the immediate aim of the enterprise.'Congress and the courts have fashioned federal conspiracy law accordingly."
CRS Report for Congress, R41222
Congressional Research Service: https://crsreports.congress.gov/