So are bombs, knives, cars, poisons, etc..
Not true, of all of those only knives are the most "gun-like" and even then not at the same level.
Bombs - require skill to make and use lethally without blowing only yourself up. They are particularly difficult to make portable enough that anyone would consider carrying them around for an impulse use.
Knives - while these are portable enough to use on an aggressive impulse and require only limited skill and strength to use they have significant limitations which mitigate a lot of their legality. They require extreme proximity, some agility and/or surprise, are easier to defend against (run away, grab any big object eg chair, martial arts, etc), difficult to use on more than one person, difficult to injure bystanders with, etc. Furthermore they have a legitimate and unavoidable nonviolent usage, so banning them would be extremely difficult.
Cars - Unless you want to run over any random pedestrian then cars are difficult to use lethally with any sort of intent. Particularly if you don't want to also get yourself killed. Mainly because cars are fairly limited by when and where they can strike (near roads) and so impulse killing is hard (except if you're nuts and want to kill randoms or perhaps run someone off the road). Again they also have a legitimate and unavoidable nonviolent usage, so banning them would be extremely difficult.
Poisons - takes skill and planning to obtain a lethal poison which you can then administer to another person. Not an impulse threat and not something most people would even know how to do well without a lot of research.