Laufey, some people are just completely inveterate pickfiddlers, and will mess with your tools, equipment and anything else that comes to hand. Without even noticing that they are doing so. And quite apart from injuring themselves because something they have casually picked up is sharp/corrosive/poisonous or in some other way dangerous, they break things. Sometimes completely irreplaceable things.
I was brought up to never, ever touch other people's stuff without a clear invitation. That piece of common courtesy and good manners seems to have largely disappeared these years, sadly. (Goes off grumbling darkly about one young man who does it all the time, and whom I can't slap down as hard as I would wish........)