I would have said the same thing before I purchased Sonos speakers for our house last year.
'Room filling sound' is very different than putting a radio in a room and turning up the sound to 11. I was blown away by the sound of our Sonos speakers. The speakers are kept at a low volume, and the quietest sounds can be distinctly heard. A poor speaker just makes the sound louder, but it doesn't increase the clarity. It's a night and day thing once you've experienced good speakers. They help you not destroy your hearing, and the costs are well worth it.
As I said overpriced speakers. Who says I have had cheap ones? You don't need to spend $400 for a good speaker that has the Apple logo on it.