i have a cube, which i bought second-hand without speakers. the cube has no audio out, so the original speakers used USB. which leaves me with 3 options: buy a pair of original speakers, which run about $70 on eBay; buy a set of soundsticks for $150-$200; or buy an ugly 3rd party set of USB speakers.
so i was investigating USB headphones, hoping they'd be a cheaper alternative. but you make a good point about USB being used for non-audio purposes... maybe i'll just get a full headset and pretend i'm directing airplanes.