Why are weapons not called guns?

I'll pile on LTC Stephen F. 's comment. Besides the definition differences there's a significant cultural and performance aspect to "weapon". A weapon is something you must learn to be competent with and use only on proper orders and within the Rules of Engagement. We expect our MILs to know and properly maintain and use weapons appropriately. Don't get too wrapped around the axle on vessels and ships. Our new Zumwalt Destroyer is longer and heavier than the WW-2 cruisers and will actually fill the role of the old Battleship in the Naval Fire Support role which was reduced. So besides all the vertical launch and other weapons systems, it's two 155mm guns are equivalent to a battery of six Army 155s. Now don't get me going on frigates which were built larger than destroyers.....

SPC Margaret Higgins I do not consider your question to be naive.
In the military guns are sometimes associated with field guns which are a type of artillery.
There are weapons which use kinetic energy such as rifles, machine and sub-machine guns and pistols and revolvers. There are weapons which are held in the hand such as combat knives and sometimes bayonets.
Similar to the navy referring to vessels as either ships of vessels - they tend to cringe if you call a naval vessel a boat.

"Why are weapons not called guns?"
I truly do not understand what you're asking with this question..
However,
Simple Definition of weapon
: something (such as a gun, knife, club, or bomb) that is used for fighting or attacking someone or for defending yourself when someone is attacking you
If you are looking for a literal response, than, All guns CAN BE weapons, but not all guns ARE weapons.
If you're looking for something else out of this discussion you'll need to be a bit less cryptic general and limited in your question

I realize that to some, this is a "dumb" question. Maybe even idiotic. However, the only dumb question: is the one not asked.
If I knew the answer to this question, I would not have asked it.

Weapons or Weaponry is the entire set of Arms, whereas Guns, is a subset of said class. So although all guns can be considered weapons, not all weapons are guns. As others have said, knives, swords, etc.

Gun is a type of weapon, sword is also a weapon. Like a car, plane truck and train are all types of vehicles. Thats the way I see it anyway.

Like others responding to this, I'm assuming that by "weapons" you are referring to firearms: Rifles, pistols, et al. In the broadest sense all are guns.

gun
ɡən/
noun
1.
a weapon incorporating a metal tube from which bullets, shells, or other missiles are propelled by explosive force, typically making a characteristic loud, sharp noise.
synonyms: firearm, pistol, revolver, rifle, shotgun, carbine, automatic, handgun, semiautomatic, machine gun, Uzi; More

However, "gun" is too imprecise for military or police use. Thus, those who work with "guns" tend to use more descriptive terms. Knowing what you are up against can save lives.

I consider all "guns" to be Weapons, because they still fall under the category of being Weapons. I, personally, find the word "guns" to just be used to classify the type of weapon, but it is commonly used in the Media as something used to terrorize people, which is why I don't like the use of the word "gun". To sum up, Weapons are, by definition, "A weapon, arm, or armament is any device used with intent to inflict damage or harm to living beings, structures, or systems.", but "guns are just a lower classification of a TYPE of weapon. By calling all weapons "guns", you are making yourself seem rather naive.

i'm am applolgizing in advance go to the movie platoon " this is my weapon this my gun one is for pleasure and one is for fun" but to be more correct guns are artillery and naval where weapons are what you persopnnally carry into combat

While there have been many definitions posted here about what constitutes a 'gun', we need to also define 'weapon.' I offer the inclusion of propaganda as a weapon. The saying "The pen is mightier than the sword" can be true in many cases. Media such as print and broadcast(Hanoi Hannah, Tokyo Rose) can be used as weapons too.