But content rules. I have 8G of mostly-mp3 music in my Google Music account simply because that's how I got it. Players out there play mp3 because that's what is out there. Of the successful consumer platforms out there, only Android includes ogg support out of the box, and that mostly due to the whims of its developers than any real market pressure.
It's exactly that point that Stallman was talking about in 2001 -- despite having very good software available, we're now into our second decade of "free software products cannot play music by default". Maybe we should have listened to him more carefully...
Around the mid-2000's, iRiver sold an OGG player, though it was $300 alongside a $300 iPod. Their interface wasn't as good, and it was clunky to use (I bought and returned one). It fell through the cracks like a zillion other iPod competitors.
Also recall DRM was a big part of digital music for a while. iTunes was dominant, and made ACC popular. I'm not even sure you can add DRM to OGG, outside of wrapping the file or watermarking. Watermarking works, but wrapping an OGG file doesn't make it OGG anymore.
So in a nutshell, OGG failed to catch on because there wasn't enough hardware or software support. On top of that, few people knew what OGG was, and didn't demand it from companies. Content owners had no reason to support it as they were focused on DRM. Apple dominated the market and standardized on MP3/ACC.
For end users I'm actually not sure either MP3 or Ogg are dominant anymore. I would guess the iTunes Store's choice of AAC has pushed that format significantly.
"Network effects": http://en.wikipedia.org/wiki/Network_effect
And if you're considering Ogg Vorbis, lets remember that the "full" name of mp3 would be something like Moving Picture Experts Group 2 Audio Layer III.
People just call them by their file extensions.
Some file types just get an easy ride, like jpeg/jpg. Imagine if it was actually routinely referred to as a Joint Expert file. Maybe pngs would have taken off faster (they are still less frequently searched than gif or jpg according to gtrends).
Plus, I could play MP3 on virtually any device. Vorbis support depended on iRiver releasing new firmware, or hacking an iPod to support Rockbox.
The Hydrogenaudio forums [1] are a great place to see how the formats progressed, if you're willing to dig through the archives.
It wasn't until around 2002 that good integer only or fixed point Ogg Vorbis decoders became available.
As an end user I can't discern any difference between the two in terms of filesize or sound quality.