The Play Ogg website lists a number of reasons why you should use Ogg formats instead of things like MP3. Unfortunately, most of them don't make sense unless you buy in to the free software movement's ideologies. I think my fellow music lovers should find these two following reasons to be compelling regardless of their mindsets.
MP3 as we know it was introduced to the world back in 1994 and hasn't made very compelling advances, compression-wise, since then. On the other hand, Ogg Vorbis is a modern audio format with better tricks in its book to deliver better audio compression. So you can have Ogg Vorbis files that take up the same amount of space as their equivalent MP3 files, but sound better. Or you can have Ogg Vorbis files with similar quality to equivalent MP3 files, but they'll have smaller file sizes. Either way, you're getting more efficient use of your audio storage space, and owners of portable audio players that use flash storage know how important that is.
Speaking of which...
MP3 is a pain for gadget manufacturers. There are multiple companies claiming to own MP3 and demanding licensing fees from anyone who wants to add MP3 support to a product. Paying one alleged owner's fees doesn't guarantee that another alleged owner won't sue your pants off - and win. Wikipedia has documented these woes, if you're interested. All of this results in a lot of spending for manufacturers, and it makes good business sense for them to compensate by raising the prices on the devices they sell.
Meanwhile, Ogg Vorbis clearly belongs to the Xiph.org Foundation and only the Xiph.org Foundation, who has made it plain as day that nobody will ever need to pay licensing fees to add Ogg Vorbis support to any product. The day when Ogg Vorbis becomes the ubiquitous audio format and MP3 playback is no longer mandatory feature for anything is the day when prices on smartphones and other devices go down.
Thanks for reading. Now, please enjoy my music, preferably without converting it to MP3.