You know, it all comes down to just two things; where are you when you are carrying, and your own personal taste.
In the lower 48 states, there are not too many places that are that far from a road or civilization of some sort. Lets face it, the days of the wild west are long gone, and most of the U.S. is pretty settled. Wild injuns and griz are not that common.
And for those backpacking into the boonies, weight is going to be a critical factor in how far you go. If I am worried about attack, I'd rather have a sak for my cutting and a nice Ruger super redhawk for defense than any blade.
Emergency shelter making? In this day of cheap synthetics, what kind of shelter are you going to make that's going to be more weather proof than a plastic or sil tarp?
With a 3 or 4 inch general use knife, and a saw or hatchet in the pack, what are you going to be doing that is not going to be handled? Now this is a knife based forums, so most of the cutlery worship here is of the cult worship item, not really based in reality. Admit it guys, we're the mutants of the human race, the knife knuts. The rest of the human population gets by very well with some made in China imitation knock off of a Spyderco. And millions of backpackers get by with only a sak. In all the miles I've done in the past 50 years on the A.T., I've yet to see large knives on many hikers/backpackers.
Alberta Ed's comment is right on. We don't really need all that stuff we carry, but we carry it because of our obsession. The large knves are a want, not a real need. The two pound lump of grey stuff between our ears let us get by with a single sharp stone flake for many tens of thousands of years.
Now let me say this; I used to carry very large knives. I did. But that was in my 20's and thirtys, and I was full of vinigar. In my 40's, I shed the heavy stuff. My Randall 14 and Western bowie were sold off. I had sat there looking at them, and really couldn't remember ever using them on anything that couldn't have been done with a much smaller handier knife. I had to admit to myself that they were ridiculous overkill for a non existant problem. I went with a small puuko, and a folding saw. I almost never needed the saw.
From what I've read about most true life survival incidents, just using your head will keep you out of trouble. But most of them seem so darn stupid, I don't think a large knife would have made a difference. On the other hand, most people we would consider native populace, seem to get by with very little of our kind of gear at all. I guess they don't have the disposable income of the people on forums like this, so they get by with a thin bladed butcher knife or even a Rapala Fillet knife and an ax. Or at least the last time I was up in Canada on a fishing trip, the local Cree's we using that combination of cutting tools, a light slicer and a hatchet or ax. The only big chopper knife around was another fisherman from the 'states who had one of the 7 inch RAT things. The two Cree guides muttered something to each other and laughed, and I had the impression they thought the big knife guy was a fool. I have a feeling that you could drop one of those Cree guides out in the boonies with a fillet knife and a hatchet, and come back in a few months, and he'll be sitting on the front porch of a cabin eating some smoked whitefish.
Each to thier own, it's a free world. But you have to seperate the needs and wants. A Porshe 911 is a want if all you need to do is commute to work. But if you just want it, and can afford it, then indulge yourself. But if your wife is only working part time because day care costs are sky high, and your kid needs braces, needs take right-away. A Honda or Toyota will do very well. It just won't be as soothing to the ego.
Needs vs wants, ego vs Id, you have to ballance it out.