I don't see why anyone needs more than one or two, if that. You obviously 'collect' guns. Lots of people 'collect' guns and other shit. Collecting shit doesn't interest me and never has. We're talking in terms of what is needed, gun-wise, by those who 'need' guns. One or two at the most, in my opinion.
Ok, allow me to point outthe flaw in that. Then, perhaps, you will have a better understanding of gun collections.
I hunt deer. For that I use a rifle. It must a be a large enough caliber to quickly, and humanely kill a 150 to 200lb animal with one shot. I prefer a .270 for that. My daughter hunts as well. Not liking the recoil, she hunts with a .243 caliber rifle.
I also hunt coyote. They are an invasive species which is wrecking havoc on native species all over the southeast and cost farmers their livestock. They also kill pets. For this my .270 is only marginally effective. The fact that I have a semi-auto for this purpose has allowed me to double the number of animals killed on several occasions (quick second shot and all). This is pest removal.
I also hunt quail. For this I have an over/under shotgun in 12 ga. It is choked for quick wing shooting.
I also hunt turkey. The over/under 12 ga is not an ideal turkey gun. So I also have a 12 ga pump with a tighter choke.
When I get the chance, I also hunt feral hogs. Again, these are an invasive species and they are doing huge amounts of damage to native fauna and destroying acres and acres of crops. The .270 would work, but the idea of stalking feral hogs with a single shot rifle is a bit insane. I have a .44 revolver and a lever action rifle in 45-70. I have taken hogs with both.
I also hunt rabbit and groundhog. The 12 ga would maul the rabbit too much to be of any use. The groundhogs are too wary to get closeenoughto use either the shotgun or the .22. I have a .17HMR rifle for these. My daughter also hunts with this rifle.
I have a .22 rifle that I keep handy for any vermin or animal problems around where I live. I live in the boonies, so the potential for raccoons, possums, ect are always there.
I work out of town. My wife has a .357 revolver that she keeps in the pistol box, loaded and ready. The response time for law enforcement out here is 30 mins. So depending on them to protect her is not an option.
I have a M1911-A1 .45ACP that I take with me. The design is 101 years old, but it is still one of the best semi-auto pistols ever made.
When I go fishing I take a .22 revolver with me for snakes.
There is simple justification for 12 firearms. I own more, but obviously owning more than 1 or 2 is not nuts. It depends on the uses. And I have not even talked about target shooting or CASS competitions.
Not that I think I have to justify anything, but I think most non-gun people do not understand the limitations of each caliber or gun. Perhaps now you have a better understanding.