There is has always been a massive "invent a caliber" craze in the hunting world, right from the start. The larger manufacturers getting into it themselves over the past 50 years certainly has added to all of the confusion.
Everyone has their different reasons as to why they like what they like. Personally, I'll be paring down to one hunting rifle once that one gets rechambered, and that will be in 7x57. Am I trying to be different? Well, one could argue that this caliber is the original modern rifle round and they got it right from the start... maybe I'm just going back to the start of the craze. If I needed a second rifle? .338-06.
Each caliber has its own balance of range, power, penetration, recoil, trajectory, and machismo. The shooter can get what fits him and his scenario best.
Why not a "normal" caliber? Because no matter what it is, I'll be loading it myself anyway and will make sure I have enough. Some people aren't in the same situation and go for something that is easy to find because they don't want to bother making it or looking for it or because it might be cheap, or maybe because they want something they can replace in camp after the airline loses it. But for a lot of us, having a pile of it on hand is all we care about, and want something optimized for our particular use. Hence all of the ".272x59mm Esoteric Magnum" calibers out there.