Photography is composed of a number of niche markets: digital, SLR, Holga, large format, medium format, rangefinder, Japanese cameras, German cameras, junky cameras, expensive cameras.
I think that Leica occupies that niche that attracts different people for different reasons. Some feel that Leica continues to hew to a very traditional approach to photography while offering the best quality that money can buy when it comes to bodies and lenses.
Others buy Leica purely as collectibles with no intent to ever use them.
Some buy because they're curious about the brand and have the money to do it. Some buy because it's cool or it will make them look hip or serious.
Some buy Leica as status symbols for the same reason that some people buy full-frame SLRs.
Some buy because of the brand's durability and perhaps because their parent, relative or best friend owned and used one. Some use a Leica because they believe it's better made than something coming off of a mass-production line in China.
And some or many buy a Leica in the belief that they will become a better photographer.
I don't think it's possible to put all Leica users in the same bucket.
And Leica knows this as well, because in addition to the standard model, they've also produced a number of limited-edition collector's models.
And even though I no longer own a Leica M, a Leica can be a one-time purchase and will last a lifetime -- several lifetimes.