well a good knife user will keep it's knife sharp. I always check mine knife and resharpen them after some use, so they will be sharp all the time.

Only exception is my utility knife, which i use for cutting cardboard and plastic straps. Thats just a simple cheap that ises replacible blade's. You know the type, which you can brake and thus explosing a new piece of sharp blade. I'm to lazy to keep on sharping knifes for cardboard. Although i haven't use them much, since quite mine old job.