Driving on public roads is regulated because by doing so, the driver is a potential threat to other operators of motor vehicles. A person who owns a gun that is kept at home is not. The use of that gun in a manner that poses at potential threat to others is already covered in most areas.
Every crime used to justify gun control laws is already a crime. Under federal law and in most states, the use of a firearm in the commission of a crime is already either an aggravating factor requiring a heavier sentence or a separate offense with mandatory prison time. Gun control is unnecessary because the sanctions for using a gun in a crime are already in place. Since these laws do not deter the criminal, they serve only to allow the state to control or criminalize otherwise law-abiding citizens. As such, they are undesirable.
Of all the causes of crime, such as rage, jealousy, poverty, racial background, etc., none have been outlawed. Implements that facilitate crime -- firearms, big knives, clubs, burglar tools and so forth -- are the only things that have been criminalized or controlled and those controls have shown little or no effect on the rate or number of crimes because the criminal has already decided to commit the crime. Most criminals, even the dumb ones seen on TV, don't believe they will be caught and many of them are not. Detroit's rate of clearance in murder cases is not exactly awe-inspiring. However, since the root causes of crime are difficult, expensive or controversial to address, the easy out is to add another layer of prohibitions, this time on the tools used by criminals.
And among legislators, the desire for easy answers that cost little to implement is almost as great as the desire to receive contributions. In Texas, the most recent state constitution says: "Every citizen shall have the right to keep and bear arms in the lawful defense of himself or the State; but the Legislature shall have power, by law, to regulate the wearing of arms, with a view to prevent crime." That was in 1876. Shortly after that constitution was ratified, the Legislature "regulated the wearing of arms" right out of existence, making it crime to carry a handgun (and a host of other implements) openly or concealed, essentially under any circumstances. The traveling exemption was poorly defined and was not an affirmative defense (i.e., did not prevent an arrest). That sorry state of affairs lasted almost to the end of the 20th Century through many sessions of the legislature and occupants of the Governor's Mansion. And just because they were often Democrats doesn't mean they were liberals: look at where most of your Southern Republicans came from. These were Southern Democrats, a breed entirely apart from those in the North and as conservative as the day is long.
Curiously, we always could (and still can) carry rifles and shotguns almost anywhere we want, but even going to the shooting range or gun shop with a handgun wasn't without risk. I can sling my Beretta CX4 over my shoulder and walk into the state capitol building as long as I am friendly and non-threatening. But heaven help me if I don't cover up my Beretta PX4. The reason one seldom sees a gun in the rear window of a pickup these days is the fear the gun will be stolen, not any concern about legal difficulties.
The National Firearms Act of 1934 was proposed and enacted largely because of the gangster activities during Prohibition. One has to wonder if the United States had not created Prohibition, which spawned much of the gangster activity because of the huge profits to be made (not unlike today's drug cartels), whether the NFA would have been enacted. Incidentally, it should be remembered that pistols and revolvers were also included in the original version of the Act. It's impossible to say, for sure, because there was also a major crime wave fueled by the Depression that was another factor.
Incidentally one does have to wonder about the new breed of SBS - the 14-inch-barreled guns used by the military and police. Shouldn't these also be removed from the purview of the Act?
Finally, neither major political party has a monopoly on gun control. The Acts of 1934 and 1968 could have disappeared overnight with an act of of any of Congresses seated in the past 42 years. The restriction on new fully-automatic weapons could go the same way. As you will note, no Congress, Democrat or Republican, conservative or liberal, has done this. Any President, from Nixon to Obama, could have stood up and said, "These laws don't work and I urge Congress to repeal them." Not one did.
