"I'm not sure if I buy the "Criminals don't follow the laws so why have them theory". And here is why. If a cop pulls over a criminal type who has an automatic weapon and there is no law that prevents the use of this weapon the cop can not arrest the perp nor take away the weapon. You are right that the criminal doesn't follow the law but the law can also act as a proactive to prevent instead of just reactive after the fact. If you go buy the "Criminals don't follow laws so why have them" theory then why have any laws at all. What is the point because bad people will do what they want regardless."
Plabonte, this is so full of misconceptions that I'm not sure where to start! First, the ban only affected Semi-autpomatic weapons, not automatic weapons (machine guns). Second, since 1968 there has been the Gun Control Act of 1968, the same law that requires you to fill out the Form 4473 (yellow sheet) when purchasing a gun, also makes it a felony for a person who has been convicted of a felony to possess a firearm, so the cop you mention above HAS cause to arrest the above cited perp. The only effect this law has had has been to drive up the aftermarket price (it only affected the sales of new guns, not the ones already out there) of SEMI-AUTOMATIC weapons that "look" like true assault rifles (selective fire military arms) to honest, law abiding people!
And as to the question you asked about reasons to own one, they are alot of fun! get out in the country where you have a good backstop, and rip off a thirty round mag as fast as you can squeeze the trigger! WOW! It's a HOT to see who can knock over ten cans (not tin cans) faster! It's a challenge to see how fast you can recover from the recoil (not much, but enough to fudge your aim) and get on the next target. Sound silly? That's what the founding fathers meant by "A well regulated militia" Militia is NOT the National Guard, or the Reserves, the militia was originally meant to be every white man between the ages of 18-45, then became every man between those ages, then became every PERSON! You get the idea? "the militia" is the pool from which the military draws personnel, whether by enlistment (recruitment) or by conscription (draft), In WWI and WWII the Germans captured said they knew exactly when they met an American unit, because the 30-06 rounds made such a decidedly more threatening crack as they passed your head in close proximity. Alas, the average marksmanship of a raw recruit has deteriorated and the power of American ammo has been dialed back, so we're just one of the gang now! In fact, the Savage Arms company produced a .22 rifle called the 1919 BSA rifle! It was an approved peice of equipment for a Boy Scout! but with the advent of WWII, the BSA droped it, as they wanted to avoid comparisons to the Hitler Youth.
FYI