Windows might not be Open Source and MS business practices may be something to be desired, but they are an open platform. And when you look at the platforms that were around when Windows came to light, there really wasn't much that was that successful where just anyone could develop for it.
Even today, companies like Apple, Nintendo, Amazon, Sony, (the list is rather lengthy) want to sell you a solid product. They want everything to be an appliance to you, like a dvd player or your tv.. where you don't notice, nor care about the software on it.
An article a while back was describing why Windows Mobile and Android will, in the long run, destroy Apple in the phone market, and in the end, it will be because of the availability of applications for them. Apple and Nintendo and Amazon and so forth, want to be the gatekeepers of software and content, and frankly.. looking at the success of MS on the desktop, that approach doesn't seem to be a successful one.
Video game systems will be the last bastion of this mentality though, i can promise you that.