Dell doesn't want to go to the cost and hassle of supporting multiple Linux distros. The alternative is simple - make Windows optional extra on all your PCs.
Dell's IdeaStorm wasn't up for long before it became clear what many people wanted - for Dell to offer Linux on their PCs. But it's not going to happen. Partly for economic reasons but also partly for ideological reasons, Dell has made it clear that this isn't going to happen. But why not just take this opportunity to make it easier and cheaper for those who want to take the Linux route and make Windows an optional extra across the range? Seems a nice, straightforward solution to me that costs Dell nothing.
I just want to note that while throughout this post I'll refer specifically to Dell, it applies equally to other OEMs too.
I was skeptical right from the start about Dell making Linux-based PCs widely available. In my opinion Dell has enough trouble supporting Windows without adding more operating systems into the mix. One Linux distro wouldn't be too bad (although putting in the tech support infrastructure for that alone would come with a hefty price tag), but supporting, say, half a dozen would be expensive indeed. At a period in history when Dell is far more concerned with making more money and cutting costs, the idea of supporting several Linux distros can't be one that anyone takes seriously.
There's also a question of market. Currently 95,000 have "promoted" the Linux on a Dell idea, which is a large number in itself, but a small drop on the ocean for an OEM like Dell. Dell would need to be pushing millions of Linux-based PCs out of the door every year to make a proposition like this worthwhile. While I have no doubts that Dell would receive a huge amount of goodwill from the Linux community if it did choose to broadly support Linux, you can't take goodwill to the bank. By shipping PCs sans Windows, the customer would be free to choose the operating system that best suits them. However, to give the end user a proper choice rather than just pay lip service to Linux, Dell would need to make sure that their hardware was supported by Linux. The user would have a choice, but no support.
What about the chances that we'll see Dell shipping PCs that aren't loaded with craplets (you know, all that trialware and crippled software that you have to uninstall off a PC once you get it)? Well, the truth is that the price of the PC is subsidized by third-party software vendors who want you to have the opportunity to use and then buy their wares. Get rid of the craplets and you'll see the price of the PC go up. Fact. This is why you don't see useful open source apps shipped with PCs, they's no money in it. And that's the bottom line.