Can only assume your using either a claped out model or a very old one. Mine is quite and is powerful enough to pull the carpet up of the floor when used without the flat head. These things are beasts. So much so they are oftern used in hotels. Though there is something spooky about passing a utility room in a hotel and seeign 10 henry's looking at you.
EDIT. How are they dirty? The contents goes into a bag? You just chuck it out. No more or less dirty than a bagless model. The dysons on the other hand are minging. Why on earth would you want to see all the contents of your hoovering efforts?
EDIT2. I can't believe I'm having a discussion about a vacume clearer. I must be living the dream!