Plenty of people were buying music from iTMS before they stopped using DRM. "Fighting the music industry for your right to DRM-free music" is just an example of the Jobs' Reality Distortion Field at work.
Apple has an effective monopoly on portable music players. They have lost some grip in the past few years with the popularity of Android phones that also play music. However, the iPod Classic owned over 90% of the market for hard-disk mp3 players and iPods collectively owned over 50% of the total market around the time iTMS dropped DRM. The remainder of the market was fragmented between Sony, Microsoft, and other players. That meant that FairPlay was your only option for selling DRM-encumbered music.
That gave Apple tremendous leverage over the music labels. Nobody was going to switch from an iPod to a Zune because it meant giving up a library of DRM-encumbered music. And nobody could sell iPod-compatible DRM-encumbered music without going through iTMS (which was already the only venue for selling to well over half the market).
So they did what any rational business would do: Start selling DRM-free music through Amazon (which people could play on their iPods) and push Apple to drop DRM from iTMS. It was actually quite funny to see everyone patting Apple on the back for "fighting for the little guy."
DRM-free ebooks aren't going to happen for a while because there are still too many vendors. Barnes & Noble, Amazon, Apple, Sony, and others all operate ebook stores. If one ebook store gets too uppity, publishers can just take their books elsewhere without having to resort to the music industry's tactics.