I learned to use an axe when I was a Boy Scout... which was so long ago that Boy Scouts were still encouraged to use axes!

Belive me, when you're cutting a log with an axe, you want it to be as sharp as you can possibly get it. A razor-sharp axe cuts into the log -- it hits where you point it and it stays there. A dull axe will bounce all over the place. You are far less likely to hurt yourself with a razor-sharp axe than you are with a dull one.

The same is true of knives, too. I have a few knives that are worn only "for show" with historical costumes. I keep these so dull that you can saw on your arm with them and not break the skin. But my rule for knives is that they should either be shaving-sharp or completely rounded and dull. Anything in between is likely to cause someone to get hurt.