From Reason.com:

Josh Sugarmann, founder and executive director of the Violence Policy Center, laid out this strategy of misdirection and obfuscation in a 1988 report on “Assault Weapons and Accessories in America.” Sugarmann observed that “the weapons’ menacing looks, coupled with the public’s confusion over fully automatic machine guns versus semi-automatic assault weapons—anything that looks like a machine gun is assumed to be a machine gun—can only increase the chance of public support for restrictions on these weapons.”

He added that because “few people can envision a practical use for these guns,” the public should be more inclined to support a ban on “assault weapons” than a ban on handguns. While handguns are by far the most common kind of firearm used to commit crimes, they are also the most popular choice for self-defense. Proscribing “assault weapons” therefore sounds more reasonable.