Hartmut, you've caught me at the moment of my writing inspiration, so there you go:
To be fair here, Microsoft also rarely speak about their kernel. They promote Windows. It so happens, that their kernel doesn't even have a name!
It is clear, of course, why Linux does have a name, as it is set aside from all other kernels in several significant ways, however, I do not see a reason why it should be promoted to non-technical consumers.
Saying "Ubuntu, based on Linux kernel" says nothing to the non-tech user but raise unnecessary questions, such as "does Ubuntu release with some other kernel as well?" and "what is a kernel and why should I care about it"?
I understand that the latter question might seem important to some of us, but seriously, of what immediate practical value is this education? Kernels of popular systems are not interchangeable in today's digital world, so Ubuntu, competing not with other Linux distros, but primarily with Windows, might not win much by speaking about kernels. You cannot stick Linux into Windows, "replacing" its original kernel. Why mention a kernel then?
The second point, about not respecting the user, I must say, with all due respect to the free software ideal, has a taste of unwelcome paternalistic attitude, in that free software supporters tend to think they are bringing light to the world, when, I would argue, they are bringing light to themselves.
Linux is being developed by those who are interested in it for themselves, any calls to conquer the world fail if not at capturing imaginations of certain impressionable individuals, then certainly at bringing on any conquest-type action. We have to be honest with ourselves - most of us enjoy playing around with Linux and although certain practical reasons, like hardware compatibility, make us desire a more broad adoption of the system, really, do we care that much?
And people who use Windows - and this might still be news for some - do not feel the need to switch, don't feel they are not respected, don't care about the freedoms that we care about - and we are not in a position to tell them that they should. It is their choice. And it may be the right choice for them.
Maybe - ... drumroll! ... - they don't need the freedoms we do. And don't need not in a sense of not being aware, but genuinely don't care for them. Someone might very genuinely not care, say, for Freedom 1. And they might consciously give it up.
So, quality sells, it's just that people understand "quality" differently.
Stability is a separate issue. Stability sells - and sells well. But the thing with stability is that on the desktop it gets lost in-between other features, such as hardware support, developer support, mainstream availability, etc. Windows machines might be less stable on average, but all those other things make it rational to give up some stability for the confidence that any hardware you buy will work.
Also, Linux stability is almost a myth, at least in the absolute form it is promoted. When it comes to multimedia systems, to the desktop, as opposed to running Apache on a server, Linux looses a lot of its stability. My worst computer experience ever (!) was with Ubuntu Karmic. It is the least stable system I have ever used, freezing about once in 2 hours, not recognizing ADSL, not having sound, etc. And I hear that modern Windows is less moody and is actually stable enough to be compared to a typical Ubuntu.
So there you go. I hope this was not boring and too off-topic.
Louigi.