It depends on where you live, what you intend to do or hunt. There are a whole lot of big time shooters that don't hunt at all, so their's would be different than a hunters. Then you have many that deer are the largest game they hunt so they would only need a couple. Others may not hunt anything smaller than deer, then some my hunt everything from squirrel to elephant.
The ONLY reason the firearm industry makes so many different calibers and style guns, people buy them. If regulations said you could only hunt a particular critter with a particular cartridge, and you could only use one specific cartridge to target shoot, those would be all the manufactors would produce.
It all boils down to economics 101, supply and demand. They also have to come up with ways to keep the shooters interest in buying new stuff. Gotta make them think what's out today is way better than was available last year.
A whole lot of it is people doing the same thing I do. I decide I would like to try this specific gun for this specific hunting/shooting, even though I may rarely do that but I get a gun to do it with. Then, a few years later, I think maybe this one may be better and get that one. Prime example, I mostly shoot a 7mm Mag for long range shots on deer etc. A while back I got the idea a 280 might be better, built one and tried it, while good, I still liked the 7mm mag better. Now I'm thinking the 280AI might be better and considering building one of those. That's three rifles that will basically do the same thing and very little difference between all three. Since I don't get rid of guns after I get one, it kinda makes them seem to multiply around here.