There used to be a time when audio CD's were "
copy-controlled", like the European
Couldn't Have Said It Better CD, for example—which due to the copy-protection isn't even a proper CD, just a plastic disc that contains music. In practice, the copy-protection scheme is trivial to circumvent and a minor annoyance at best. The
Sony Rootkit scandal was the final nail in it's coffin.
Digital rights management with MP3's and other digital music has probably stopped because 99% of the customers (and a lot of vendors) don't want it. DRM restricts the way you can use the products you bought, like you can just play it on a limited number of devices, burn it to CD for an x-number of times—and then you can rip those CDs to DRM-free mp3s, etc. Basically, it's a hassle that places you deep into the clutches of whomever sells you the stuff. A company only needs to shut down it's licensing server, and
as thanks for doing the right thing and paying for your downloads, you're stuck with a pile of useless data.
(And don't start complaining most of those links go to Wikipedia. Google it yourself if you don't like 'em.)