Different folks have different ideas on such things.
Some want higher velocity, some want a bigger bullet, and some just like the sound of certain cartridges. I once ran into a fellow using a .460 Wby to shoot a buffalo. I was using a 7mm mag. In truth, I could have done the same job with a .45 Colt.
It's interesting that this unfortunate magnum shooter actually missed several shots at his buffalo at extremely close range. I'm talking somethiong like 20-30 yards, and a buffalo heart/lung area makes a fair sized target.
To be very honest, I'd feel very confidant with nothing more than a lever rifle in .45 Colt anywhere in the lower 48. I can push a 300 grain bullet to around 1700 fps, which is the equivalent of a .454 Casull handgun, but with better accuracy. I'd feel perfectly comfortable with a 45/70 in Alaska, and might even consider the .45 Colt, depending on where I was headed.
It's more about hitting your target than shooting the biggest cartridge.
Daryl