Let me preface by saying I do use Linix, and I do support opensource...
<-- begin cut
From my point of view, they have no reason not to be able to make software for Linux.
end cut -->
From "their" point of view, do they have any reason TO make software for Linux? Perhaps not, perhaps so. Microsoft is not some benevolant organization trying to make the world a better place with open ideas and code. They are a business, businesses only purpose at the end of the day is to make a profit. I know a few of the guys at Microsoft and I know that they have the resources and capabilities to create software for Linux. But is it worth the money/time involved for them? If you look at what Microsoft offers for free, you'll find that it is basically limited to plugins/applications for Microsoft Products. Windows costs $$$, Office costs $$$$$. Realistically, I don't see people in the Linux community rushing out to buy (yes, buy, MS "IS" a business) a closed source (yes, closed, see previous point), application from Microsoft. Microsoft's business is designing and selling software. Whatever you think of their skillset or business practices aside, you have to acknowledge that they are fairly successful at what they do. I would venture to say that they have researched releasing software (closed source) for Linux, but have decided that the profit margin is not there. They stick to what they do. It's worked for them so far, and I suspect it will continue to work for them in the future.
Okay, I wasn't going to say that you don't use Linux, I don't really care if you do or not. That is irrelevant, at least in my view.
I also understand that they are a business. I understand that most, if not all, businesses are in it for a profit. I also know that there are people who like Microsoft's software(They do make good software, I don't deny that) for but would like to use a Linux operating system rather than Windows(Although I don't know how many). If they wanted, like a lot of other software companies, they could make a version of their program for Linux that isn't as feature full as the one for Windows(eg: Real!'s Real Player for linux) and sell it for less. If they get a good response from the community they can update it and make it better. If they don't they could say that they tried and there weren't enough people interested(Which wouldn't surprise me if they did make a less feature full version). I think it would be a great idea to make a version for Linux, since they have competitors(OpenOffice.org, and others that I can't think of at the moment) that already work on Linux and Windows. The only reason I think it would be a bad idea is it would give people who only like the Microsoft Office suite a reason to not buy Windows(Which is a very good reason, I admit).
And, as I've stated previously, I know they're trying to make money. Just because it works on Linux doesn't mean it has to be free. They can set the cost to anything(reasonable) and sell it for Linux as well. And, as for the free stuff Microsoft offers, I haven't seen that many plugins and stuff like that. I have seen Internet Explorer(Which is free, but only if you buy Windows... Which makes sense, since you are paying for it when you pay for the license, or at least that's what I think[I haven't actually read the EULA so I don't know if you're paying for IE or if they're just only letting people who bought Windows have it.]).
IE, and a few other programs, are the only ones that appear to be free. And since, as far as I know, you need to have Microsoft Windows in order to download any programs that are included with Microsoft Windows they aren't really free. Just free to use after you've purchased their OS.
Anyway, Thanks for the reply. I understand your view and don't deny that it has it's foundation. This is just my reply, which I hope gives a little more support on my view of the situation.
I may not know everything about what MS is doing or how monopolies work, but I know that they could be doing something more competitive in the software market and they're not(While the OS is software, every piece of software that is run on the machine interacts with the OS and therefore I believe it shouldn't be put in the same category).