Why are Chainsaws Used Against Zombies?

I always believed that it was because the chainsaw makes it easy to take off the zombie's head which kills it. If one has a sword or an ax, one has to have a mighty powerful sword arm to take off the zombie's head. If one has a gun, one has to score a headshot to kill the thing. Also, a chainsaw could be used to take off multiple zombie heads at once. That's just my opinion. I love zombie movies!