I agree with Frenchy (BTW my Dad's nickname)
For EDC I'll take my 4" framelock, or even smaller (my current EDC is the largest I've ever carried)

I think the original poster's question is more along the lines of "why the heck to people carry such BIG knives out in the woods"

I see a LOT of folks who walk around with a 9-12" blade knife. WHY? If your going to carry something that big, your probably a LOT better off with a smaller knife and a hatchet. In fact, that was my compromise for years - a 4" fixed blade on the belt, with a hatchet on the outside of the pack (and there was always a Boy Scout knife in my pocket - it was my EDC for years - pre leatherman)