Because the difference is purely cosmetic. Nobody is arguing for unrestrained possession of automatic weapons -- aka "machine guns." And the difference between your basic hunting rifle and what people refer to as "assault rifles" is simply a difference in stock, sight and magazine. Imma gonna hold my nose and, as much as I hate to, link to Fox News. Because even a broken clock is right sometimes, and this is one of Fox's moments: http://www.foxnews.com/politics/2013/01/16/gun-debate-what-makes-gun-assault-rifle/
If the difference is "purely cosmetic" why is it that nearly every state limits magazine capacity to five if you're hunting? Ever ripped through a 30-round mag with an AR-15? I have. It's hella faster than ripping through three ten-round mags. And that's when you give a shit about what you're shooting at, not doing the dumb-ass Rambo trigger finger trick. Peruse the North Hollywood Shootout for other "cosmetic" differences; those "cosmetic" differences are why the cops in my 'hood sport S&W 40s and Benelli M4s and AR-15s and body armor. So now, when somebody gets pulled over by the airport, they're covered by the same amount of firepower and the same attitude as Marine Recon in Baghdad. Which is hardly "cosmetic."The patrol officers were armed with standard Beretta 92F and Beretta 92FS 9mm pistols and Smith & Wesson Model 15 .38 caliber revolvers, while officers including James Zaboravan also carried a 12-gauge Ithaca Model 37 pump-action shotgun. The officers' weaponry could not penetrate aramid body armor worn by Phillips and Mătăsăreanu, which covered most of their bodies and provided more bullet resistance than standard-issue police Kevlar vests. The robbers' heads were the only vital organs that were unprotected, but most of the LAPD officers' service pistols had insufficient range and relatively poor accuracy. Additionally, the officers were pinned down by the heavy spray of gunfire coming from the robbers, making it difficult to attempt a headshot.