The main reason anything is marketed as a 'Leica-killer' is the same reason something is marketed as an 'iPad-killer'. It's to get the word 'Leica' into the ad copy, so, when someone searches online, your page comes up.
It's a kind of tacit admission of defeat, but, if it brings a few customers their way, just like those annoying eBay-sellers who put 'Not Leica, Zeiss...etc etc' into their descriptions, then it pays its way as a tactic, sadly.
As for the unique position of Leica, I love using a mechanical rangefinder in my photography, as I find it harder to focus an SLR, and autofocus is fiddly to control if you're not just going to give it its head (OK, so that's what I generally do with my m43, but it's not ideal). And I would love to have a full-frame digital camera that isn't as bulky as the DSLRs. The only FFRF is a Leica, so what are my options? If there were to be a digital version of the ZIZM, I'd be over the moon (and in trouble with my partner for spending a lot of money we don't have). But there isn't.
Leica may spend a lot of time and effort making rich men's toys for the luxury gadget market, but they also make damn good cameras, and the PR they get keeps them positioned as a key luxury brand.