Luscious, allow me to present an argument for Apple's case. First, they can succeed with the iPad simply because they market their products excellently, better than any other technology company today. No one in the US today doesn't know what an iPad is; it's been in the news, commercials, TV, radio, online...everywhere.
Second, Apple's on a very hot running streak with excellent products. Their notebooks sell extremely well, especially to students. Schools are picking up iPad deals, and they may well replace many current school's first choice for that "thing to give new students".
Third, even if Apple's platform is closed to developers and restricts them heavily, they also offer the largest app store and media store online anywhere. Sure, the iPad can't compete with a Windows 7 tablet in terms of the sheer number of applications, but once again the iPad is oh so different from what we've seen of products like HP's Slate. And, suffice it to say, Apple released their product first. If they hadn't, they could have been on the opposite side of the fence on the tablet market.
Finally, yes they have left many blank areas in terms of their hardware, and yes they have proved their arrogance time and time again. And yet they still succeed. In a strange, unforeseen way, people like that about Apple. They like that Apple can say no to just about anything. Because to Apple, it's ultimately the end user experience that counts the most. Users don't really want to sit there and swap SD cards between devices or plug their iPads into every computer they and their friends own. It's a standalone device that is meant to do everything wirelessly, and taking that away by adding a built-in card reader will only sacrifice their true beliefs about the device.
Then again, they offer the media card inputs, because they are still in the business of making money. Which is also why the starter iPad is $500, not $300.