Because combat knives are really high quality utility blades, most of the time anyway, that may be just happen to be suitable for fighting if you happen to be out of bullets or don't have a baseball bat handy. Rather than turning yourself into a bloody pug rag fighting someone knife to knife they are much more useful for things such as constructing shelter, shaving fire kindling, skinning animals, cutting food so you can eat, opening cans, boxes, cutting rope and bindings, constructing things etc....
I do like the coolness factor as well even though troops are supplied with better quality equipment than civilians, trucks, vehicles, electronics (all built to a tolerance of 10 vs civilian 1.5) and yes troops are generally issued better quality knives than you standard kitchen knife or pakistan crap either of which would have not problem penetrating human flesh some of kitchen variety are so thin and sharp they would penetrate clothes even better than the so called combat "fighting knives." I like quality knives do you?
So what gives you say tomatoes I say tomotoes, I say extra cheese you say hold the pickles.
I say why should a particular syle of blade suited to somes tastes be called "killer steels" or demonized or whatever.
It all boils down to because I like it a lot. I see it this way even if the knife was designed as a weapon, knives used primarily as weapons in this day and age is so antiquated and outdated it really should be a moot issue. You have sticks, bats, kithchen knives, chain saws, chains, axes, bottles, motor vehicles (ok you do need a lliscense and registration for cars,) bricks, rocks, dogs (yea they need to be liscensed also,) the list goes on and have your pick the bad guys will use anything but for the most part why when you can get a good ol gun and that will put all of the above moot.
Maybe someday we will be required to have a permit for almost anything that can be used as a weapon. Should we turn the cities into semi prisons (only plastic knives and spoons allowed in your kitchen ect...)