Could it be because most people by now have figured out the Levinson "house" sound and don't like it?
I have heard ML amps in three different systems and never cared for the sound any time. Now it might have been something other than the amps, but they were the only common denominator
I'm not a believer that solid state amps that measure similarly sound significantly different. I know that's heresy to some, but the value proposition (at least for me) for amps like Levinson and Krell is that they act like consistent voltage sources with low distortion and low noise into low impedance or highly capacitive loads. Not too many amps can do that. They also have very low distortion at sub-1W output. These are differences which are known to audible. But I don't understand how there can be a "house sound" signature that can't be measured.
Just thinking about it, it might be that the economic situation in the US is hitting people who tend to spend a lot on high-end audio pretty hard, reducing the market. ;-)