I use a desktop (or laptop) for doing work. The most I will do on my phone is send a short email reply, as the interface is so inferior for getting any "real" work done.
And neither are you or the OP. In fact, I'd hazard a guess that you are in actual fact a minority. Before you assert higher mobile sales again, think on how many people use their device for anything more than the very basics; photos, messaging and social networking etc.
No one is trying to tell you you can't use Word to your heart's content on your own machine. When you send email to another person, though, you can't assume that they're going to have it. Especially not now.
"In fact, I'd hazard a guess that you are in actual fact a minority."
Smartphones that do have email and don't have Microsoft Word are a minority?
How do you figure that? Neither iOS nor Android comes with the ability to view Word documents.
You're absolutely right, in the comparison you choose to set out.
I was probably being vague: I wasn't really looking at this in terms of mobile/desktop usage, more considering the average HN readers's expectations of the non-HN reader's technology preferences.
They like Microsoft Word, and there's more of them than us.