I coach sailing so I usually have a sog multitool, a boxcutter, and my trusty sog trident with me at all times. Whoever says that knives are stupid clearly doesn't work outdoors or in a location that they are needed. I use each and every one of them on a daily basis. Boxcutter for cutting fabric, the multitool for screwdriving and cutting wire/cable (shouds on the mast and stuff in rescues) and the trident for just general use, rope cutting etc.
I do agree however that it is stupid for kids to be carrying around knives to school and such, but I almost always have my trident with me, just in my backpack at school.