I"m going to go ahead and disagree that Linux isn"t a pita. You guys use it every day, and are familure with it. There is a learning curve, and the OS still isn"t user friendly enough.
There are kind of two points here, one I agree with and one I don"t. As far as the software itself is concerned, the main barrier is the learning curve. But not that it"s too steep or difficult, just that it"s there and visible. Windows moves slowly enough that people don"t notice they"re learning as Microsoft changes things – or just put up with it because it"s what they"ve always done. I don"t agree that it"s a PITA for the things people who don"t know anything about Windows use their computers for.
I don't think it's any different than a lifelong Windows user switching to OSX, if you cut out Apple's brilliant brainwashing. It's very different, some things will be frustrating and difficult, and you need to adjust your perception of how the computer should work a bit (well, a lot, if we're talking about OSX).
As far as "plug in and work", I don"t know what distros you"ve been using, but these days most new hardware will, in fact, be "plug in and work". Might not work as you"ve grown to expect on another OS, but that"s a different thing.
Last night I installed Samba and miniDLNA on my NAS through the CLI, how many users out there even know how to use the CLI?
Both of these things are trivial to set up in Ubuntu and most distros that care about user friendliness. And they don"t involve CLI. They don"t involve randomly searching the web for applications and downloading malware and toolbar ridden crapware either. Go to Ubuntu Software Centre, search for "DLNA" and install the first option (Rygel). Comes with a GUI config tool. For Samba, search for "Samba" and install it. Comes with a GUI config tool.
As far as install location – let the package manager deal with this. The way it"s handled in Linux is different, not a problem. In fact, I"d say this (proper unified package management) is one of the biggest and most important things that Linux has to offer.
I get the notion that you haven't actually sat down and seriously used a consumer-oriented Linux for a while in a long time, or ever. Go download Ubuntu or Mint or SuSE (or probably Fedora, but I haven't touched RedHat-based stuff in a decade) and give them a try. I think you'll be surprised.
Anyway, on topic. Yes, Canonical could pare down Ubuntu and release a special Raspberry Pi edition. But what"s the value in this? It teaches people to use something that"s not Ubuntu. It gets users thinking Ubuntu when what they"re really using is a half-cocked version of it they"ve cooked up to fit in the hardware. And it"s not going to be the same as what they use when they install Ubuntu on their desktop, which is probably worse than them never having touched Ubuntu at all before installing it there.
It just doesn"t make sense. Maybe in a couple years when the cheap hardware that"s available is powerful enough to run the same OS as you"d run on any other machine, but for now all it would do is dilute their brand with a different and (in their eyes at least) inferior product.