Discussed many times and at length. Truth be told IMHO opinion, I don't think there's any such thing as the perfect knife, be it for any scenario or any group of people. There's just toooooo many variables...everything from terrain/environment to intended usage...to user's skill and capabilities. I will say that when I recently commissioned a custom all-around outdoor/camp knife from NWA, I specified a ~7 x .25" blade of differtially heat treated steel, so that probably gives you a good idea on what my feelings are. I am a big believer in that a bigger knife can do things a smaller knife can do...maybe not perfectly well, but can manage through it 'good enough.' I don't think the reverse applies as frequently (a small blade doing a large blade's job).
Again, what you 'need' has sooo many variables. A guy camping out of his 25 foot trailer with flat screen TV is probably going to need alot less than a guy 5 miles off the trail with only his pack on his back.
For me, I take what I feel would get me through a bad scenario out on my excusions (I don't have a trailer)...that is getting hurt and not being able to walk out for a night or longer. That's my 8" bladed NMSFNO. Will I use it 99% of the time on my outings? Nope, probably not unless I'm just screwing around for fun. But if I twist my ankle and need to bed down for a night, It'll help get a shelter built, prep some firewood, etc. That works for me in my area with my skills and capabilities. YMMV. Could I probably do with less? Sure? More? sure. But to me, the NMSFNO is the best balance for my anticipated needs and usage...which I think is a solid arguement. A knife should not be so large/heavy/unwieldy that it outweighs its value. And again, that's gonna vary for everyone on alotta different factors.
And as others have chimed in, part of their enjoyment of their experience is carrying a particular knife, be it large or small. They may not need it for use, but they simply enjoy having it, and since its their time and their dime, who is anyone to judge and say they shouldn't have it? Unless its something that is going to harm you down the road, have at it I say.
And FWIW, there's LOTS of places where one can get lost and find themselves in a sticky situation. How far can you hobble, or worse, crawl, injured, across uneven terrain? Sprain or break a leg/ankle/knee etc. and if you're by yourself and don't have cell coverage in a remote area, and you could be in some trouble faster than you think. Plenty of SAR teams keep busy rescuing or recovering folks not too far off the beaten path.
As to the mountain men of the 1800's, yes definitely a tougher lot than the "I want sprinkles on my latte and a flat screen' crowd of today. I must confess, while I don't have the flat screen, I do like lattes, but hold the sprinkles. But lets not downplay alot of those folks died out there...they went out and never came back...starving, exposure, injury, murdered, etc. It was just more accepted as part of life back then. It didn't make the national news.
Just my $.02 worth.