Why so many Hegel's for sale?

Simple, integrated units are just a step a long the path. People decide they want something more and move up to separates. They rarely go down or even sideways. Not that Hegels are bad. They are not bad at all.
Millercarbon the reason there are not Moabs for sale is that nobody in their right mind will by them in the first place. When they do show up it will be for pennies on the dollar. One of the worst designs ever perpetrated on the audio market.

Now I'm gonna get it  🤕

while very very good pieces do show up more rarely on the used market than less good ones, to say they NEVER show up is overly simplistic and inaccurate

words like never, perfect, always, best are too absolute and extreme to describe most reality, unless you are dealing with immutable laws of physics or matter - often not applicable in the hifi world

audiophiles with money randomly trade away really great stuff often... always chasing something they THINK is better... a good portion of the time they are wrong... same with the luxury/enthusiast car market... some cars lovers just sequentially change cars from pure boredom, then they post on car forums how much they regret selling ’x’ car, wish they had it back

also, people get laid off, they get old, they get sick, they die... and their treasured pieces get sold off

The number of used units offered for sale depends, above all, on the size of the manufacturing company and their degree of market penetration.  B&W speakers are a good example; there are many others.  Paradoxically, then, this would, at least in part, be a sign of Hegel's success.

There are always more than a few Vandersteen speaker's for sale.
Does that mean they're lousy speakers?