iTunes TV Store?

I love my Apple TV. We turned off Cable in the early summer in favor of using just and Apple TV, the iTunes music/tv store and Netflix to get our content. There is just one thing I don't understand about Apple TV? If Apple can build the iTunes music store for the iPhone then why can't they build an iTunes Music/Video store for the Apple TV? I can't tell you how many times I have wanted to buy a new show for my daughter and have had to run upstairs, buy the show, download it to my laptop, and then sync. Really, all I want from Macworld is the ability to buy content directly from the Apple TV. Preferably without having to buy a whole new unit too :)