Why is the market for used Levinson amps so slow?

I don't think we have established that there is a problem. I've owned seven ML components in the past 15 years and have had no reliability problems, other than when two fuses blew in a power amp, do to my own incompetence. I recently traded up a #431 for a #532, the #431 was sold before it arrived at the dealers and for three quarters of the new price. Most of the responses above seem to be speculation rather than facts.
One other thing to consider is that back in the day, there were three undisputed high end brands Levinson, Krell and Roland, there was much controversy about which was number one but it was always one of the three. Now there are more great brands that you could name.

Tmsorrosk,
The ML amp issues seem to center around the 300 series model(bad/poor quality capacitors). Your amplifiers are a different series/model and likely used better caps. I`m sure not 'every' 300 series amp owner had problems,but enough did to make this a legitimate concern.

Tmsorosk, first of all, it's Rowland, as in Jeff Rowland. Secondly, no it wasn't the big 3, everyone knows that no high end SS list is complete without Nelson Pass and his Threshold/Pass designs. Some might argue that Boulder and others deserve to be on that list too.

Also, that is just a list of high end American SS designers. You also have high end SS from other countries. I won't even bother to start listing high end SS international brands.
So it definitely WAS NOT always one of those 3 you mentioned as to who was number 1. They were/are 3 big names, let's just leave it at that.

Charles1dad,,, I have heard of some problems with the 300 series and as you said not everyone had this problem, infact I might suggest that only a few had a problem. My #332 was 10 years old when I sold it to a friend, it's still working without issue. Also had two friends with the same series that had no issues, sometimes things just get blown out of proportion, the internet hasn't helped.
It probably helped that the units in question were not turned off.

Jmcgrogan2,,, there were no doubt many other great brands, but if you asked 9 out of ten audiophiles what were the top three brands you would get that response. Rightly or wrongly so.

Tmsorosk, I humbly agree to disagree. I will agree that Krell and Levinson spent the most money on advertising and marketing, but you can't convince me that Rowland was a bigger name than Threshold 'back in the day'.