As I mention in my article, what you say is true, but hasn't stopped iOS apps from taking off. Yes, many people won't be able to use Mac OS App Store apps because they don't have Macs, but that won't be a problem to the web developers who switch to Mac, because they'll be willing to make the trade-off based on the hype and numbers that the Mac Store achieves.

Not everyone has a Mac, but enough people have one to make it worthwhile. And those Mac owners actually buy apps, unlike the vast majority of windows computer owners.