Well, historically the knife served as a secondary weapon in the era when guns were one-shooters. Now with the invention of reliable repeating firearms, I tend to think of the gun as a weapon, and knife as a tool. Most tool uses don't require a 12" blade, in fact it gets in the way.
That said, nothing wrong with carrying more than one tool. For me, Buck 110 or Case equivalent sheathed on the left side, small two blade jack in the coin pocket on the right.
I spread mayo much more often than I gut a deer...
Parker