I suspect the realities of electrical engineering plus economies of scale are conspiring. It's cheap to build really good amps using proven techniques, and so we keep doing it.

Digital amps, despite what some more vehement supporters asserted almost a decade ago, are hard to make right for an arbitrary load. *I* had hoped we'd see more self powered speakers and within those, class D amps that were precisely matched to the driver they powered. No dice though.

I do find the self powered Martin Logans intriguing though.