I think the real motivation behind this is to [...] make what you can buy colourful and what you already own bland.He hit the nail on the head.
From Apple’s point of view, the iTunes/iOS ecosystem has reached a level of market penetration where the focus has shifted away from improving the app and moved more toward exploiting the app’s ubiquity to sell more content.
Since the introduction of the iTunes Music Store, Apple has made each release of iTunes more focused on directing users to stuff they can buy. Here’s just one example: If you click the little gray arrow to the right of an album name, you might expect iTunes to take you to that album in your own music library; but instead, it redirects you to the album in the iTunes Music Store.
Here’s another example: the Ringtones button reappears periodically in bottom row of icons in the iOS iTunes app, and the Podcasts icon disappears. The user can change this, replacing the Ringtones icon with the Podcasts icon; but after a while, it will change back again. Again, this has the effect of directing you toward stuff you can buy (ringtones) instead of stuff that’s free (podcasts).
And one last example: it is not possible to have iTunes save your password for free downloads only. If you want iTunes to save your password, simplifying the downloading of free apps, music tracks, and podcasts, then you must also have a valid credit card on file, and allow iTunes to save your password for purchases too.
Apple’s engineers are well aware that bland, colorless portions of the UI are less likely to capture and hold the interest and attention of the user. This is by design.
From recent updates to the iTunes app, we can infer the following design objectives:
1. Reduce the user interface to its spartan, utilitarian minimum, and focus the user’s attention on the content area of the window;
2. Lead the user quickly to purchasable or promotional content in the Store, and do this from as many places in the app as possible; and
3. Make it as easy as possible to purchase content.