I'm not referring to that type of support; this is merely support for the base platform. I'm referring to the entire ecosystem of Microsoft products, of which you'll find most are x86 only.
When you say "there's no money to be made...so Micosoft has no reason to bother", this attitude is a major reason why ia64 failed, and why their previous arm attempt failed, and why their current arm attempt is also likely to fail. If the software isn't there, it's a poor proposition for most customers.
When I run Linux on ia64 or arm, I have an entire distribution's worth of software at my fingertips, and for the most part I'm not losing out compared with more popular architectures. With Windows, no matter how technically good the base platform may be, the ecosystem is a wasteland and will remain so until Microsoft put the effort in to support them properly.
Supporting multiple platforms is not expensive; it's simply a matter of having the build infrastructure in place. In Debian we had it build every package automatically built on 11 platforms. Microsoft could do the same for their applications. For example, see https://buildd.debian.org/status/package.php?p=okular&suite=... -- one package built for 22 platforms. Building for three or four is not a lot to ask...