I think you're right, and it makes me sad. Who would prefer a distorted image over a non-distorted one, black bars or not?
The only explanation I have for this is sense of entitlement: "I paid dearly for each of these pixels so you better use all of them, no matter how bad the picture looks like!"
This is a feature not a bug. Most people don't understand aspect ration and in fact will get upset if a standard def video doesn't fill the HD screen.
Actually, it is probably just laziness on the manufacturers part but it works out well for most consumers.