I hate

I find it worrying that someone feels the need to carry a knife unless you live in Alaska, Canada or Siberia.
Where do you live?

There are plenty of reasons to carry a knife. Well, actually there is one reason to carry a knife, you need to take it somewhere to cut something. As long as you have a lawful reason to cut that thing (a chef carrying knives to a place of work, a caligraphy enthusiast carrying a pen knife to cut a feather to make a quill, an outdoorsman carrying a knife to gut a fish that he expects to catch) then really there can be no reasonable objection.

Generally carrying a knife on the expectation that you might have to cut something at some point but don't know what it is yet isn't really justifiable though. As is easily demonstrated by the fact that the vast majority of the bladeless get by just fine on a day to day basis.

Still the difference between guns and knives is pretty simple. Knives are tools, guns are carried by them.