Fine furniture is expensive- the wood used can be very pricey, might even be restricted by the Lacey Act, which prohibits selling/shipping certain species that have been placed on the 'protected', 'endangered' or procured illegally.
If they could find a way for exotic materials to improve the sound from speaker cabinets, it might be seen as a good reason for using them but the fact is, they don't. OTOH, I hope nobody makes bedliner the official cabinet covering material.