Your analogies don't really hold up. Consider:
Cars do require certain attributes to be legal, such as meeting safety regulations. Also, traffic laws, including speed limits are indeed laws which put limits on behavior regarding the use of cars. How about behavior laws for guns, such as when and where you may use one, have one on your person, how many bullets you can shoot, etc. Remember, not only is your behavior with cars limited on the roadways, but it is also restricted to roadways. Last time I checked, nobody is going to approve of you driving your car through a playground, a park, a department store, or a movie theater.
My argument is to not add new laws. There are safety regulations when it comes to guns. Every gun has some sort of safety feature on it (at least one). Every gun is shipped with a lock to keep it out of the reach of unauthorized people. You can't be drunk and discharge a firearm in most (if not all) states. Concealed carry licenses in Florida don't allow the carrier to go into a restaurant that serves alcohol, a sporting event, or a government building. Not to mention it's very illegal to use a gun in a crime, especially to murder (at least in Florida).
You've said that guns serve no other purpose than to kill (which isn't true, but we'll go with it). My analogies show that there are things out there which have no purpose other than to put people in danger, such as the ability for cars to far exceed the traffic laws. Even little 4 cylinder cars have the ability to go 100 mph, which is illegal on public roads and can be extremely deadly, moreso than a car restricted to 70 mph.
My point is that just because somebody could do something bad, or has done something bad, with an object we shouldn't necessarily be focusing our attention on the object rather than the person behind it. We don't say "If only cars were restricted in speed, we wouldn't have these thousands of speed related accidents." Nor do we say, "If only alcohol didn't exist, we wouldn't have parents beating their children, people destroying their livers, and kids getting run over by drunk drivers." We say that drivers should slow down and that drinkers should be responsible in their drinking.
Essentially, what I'm saying is that while we have things that are completely unnecessary and are responsible for more deaths in this country, we tell people to use them responsibly and blame the operator for it's use. With guns, especially "assault weapons" we tend to blame their existence for the damage they cause.