This is my favorite post from the comments section:
A knive is ridiculous as a ten essential to backpackers as you carry your shelter and warmth and unless you need to slice cheese a knive is silly. Having said that, the 'knive' zealotry is so entrenched in otherwise smart people, that I'll bet everyone will disagree with me but I challenge you to tell me what you use a knife for when backpacking. I do believe in a heavy duty scissors tho. Cheers
Posted: Nov 06, 2010 Babettezz
I have encountered a few backpackers that do not carry knives. The areas they hike into and campsites are heavily used. They also carry just about everything on their back (all the gizmos and gimmick items). Their gear is specialized and not multi purpose oriented. Civilization is not too far away on these trails and as a result encounters with people on a daily basis is standard.
I imagine the scissors is for cutting mole skin, bandages, duct tape, plastic wrapping on salami rolls, the bags of Mountian House meals, etc...