Of course it is about choice for the consumer. And Apple don't like their consumers to have it. The whole point of DRM is to prevent piracy, not tie one product in with another. You want ITMS music on the move you have GOT to buy an iPod.
You have choice. It's not like iTunes is the only music store around. If you don't like iTunes, you can always buy from some other music website.
All consumers want choice and somehow Apple seem to get away without having to provide it. It uses it's software products to protect it's hardware sales. Don't agree, then why do they produce software to let you boot an intel Mac to Windows, but vigourously prevent you from running OSX on other Intel based systems.
That's simple. OS X exists to sell Mac Hardware. Apple is primarily a hardware provider, as witnessed by their revenue breakdown. You want to run OS X, run it on a Mac. Having OS X running on a bog standard PC is to compete with MS's business model, i.e. providing a generic OS to run on generic PCs. You'll also inherit the headaches MS has, of having to guarantee compatibility with a wide spectrum of hardware (most windows crashes can be attributed to poor drivers), guarantee a stable binary interface (something OS X is kinda notorious for not having), all for very little returns. After all, most of Apple's revenue comes from selling machines, not copies of OS X.
You always have a choice, of course. You can choose not to use OS X, in the same way that you can choose not to use Windows or Linux. Allow for a very poor car analogy. It's like wanting to have a Ferrari engine in a Fiat, and then complaining that Ferrari refuses to allow their engines to be put into any other car.
Apple's business model is substantially different from Microsoft. They see themselves as a solutions provider. As such, they seek to fill the entire computer stack, from hardware to OS to user level applications. Call it vendor lock in if you want, it's just a different business model from your usual PC manufacturer. If you disagree strongly enough with it, just vote with your feet. Everyone who advocates providing the ability for running OS X on just any PC, or running iTunes music on any player never ever provides a solid financial reason for doing so, other than "because that gives consumers choice" or they point to examples like Microsoft and wonder why Apple doesn't adopt a similar strategy.