I never said Dwarves couldn't do that. I think it would be a good trade off for the dwarfs.
I like the idea of monster exploitation. It makes adventuring much more interesting.
Imagine, adventurers coming to an ancient tomb, finding a massive tentacled beast with a thousand mouths guarding a gate to a realm that should not be. Their first thought? "Dude, it'd make a killer telephone operator. We just have to capture it, teach it to speak and enslave it, then we're golden!"
In fact, you could have an entire breed of adventurers like this, they would function less as treasure hunters and more like monster wranglers - they go to dungeons, get all sorts of cool monsters with special slave collars, then try to sell or utilize them for commercial ventures.
No. And I only say this knowing how horrible that would be for the monsters. So to compromise I say they are treated like slavers.