It's not "the MA thing" so much, it's the reality is that people who have those things have money. People who have money generally find that selling guns is kind of annoying and generally a huge waste of time, even if they don't need the gun, they'd rather just hang onto it.
I kinda spoke about this in another thread- "transaction cost". When people get busy the value of time becomes more and more apparent- and a lot of the guys that have a lot of money, also often have the least amount of free time. The dude with the AI that goes shooting 3 times a year, the guy that would sell it but doesn't need the money- if you really want that gun you better be close friends with him and do it at his convenience, because pretty much anything else is kinda costing him money or already past the threshold of annoyance.
-Mike