So it's unacceptable that Microsoft hasn't done it by Windows 8, but it's OK that apple didn't do it until OSX - i.e. 10?
Some may see it as convenient, but not everyone. Again, it's done for control and money. Convenience to any user is just a extra bonus for them. You do realize Apple has used this to keep people from writing things they don't want them too, right? Your browser can use flash? Banned. You want access to the music files? Banned. Doesn't meet the moral level? Banned. Furthermore, they locked everyone else OUT. You get it from the app store or you don't get it - unless you're capable of jailbreaking. That's very problematic.
Now, if you want an app store that's simply a clearing house, fine. No moral checks, no policy checks, no agendas, and simply code validation and distribution that'd be fine. But it shouldn't be app store or nothing.
Apple, or more accurately, Steve Jobs had a personal issue with adobe, so he banned flash. Microsoft could use their app store to ban stuff too. Only problem is all the US and EU and who knows who else would yank them into court ASAP and they'd be hit with mega fines. But, as long as it's Apple banning things - it's OK, right?