I don't think they're trying to make the experience worse for users per-se, but trying to drive customers to use the native Apple applications.
Why?
Here's my theory. Let's say you have a fantastic application such as Web Albums HD (I'm assuming it's fantastic for the purpose of my argument). Then presumably once there are competitive tablets on other platforms, the developers would port their application to other platforms. The user would say, "Gee, I can get this application on any platform. So what's the big deal with the Apple tablet".
But if you end up primarily using Apple applications because they are the only version available due to app store restrictions (web browser, email, voicemail) or they have a superior experience due to app store restrictions (photos, ebook readers), you'll be less likely to switch to another platform.
Although, by using these techniques, the end result is a worse user experience, which seems very anti the Apple I knew. (I say this as a former employee)
I can understand Apple refusing apps where the experience sucks, but forcing developers to modify their app to make the UX worse than Apple's bundled app seems a little ridiculous and anti-consumer.
