Some of the suggestions to do with MMS being obsolete are downright ludicrous. Maybe this is the difference between the UK and the US market. In the UK I can safely say that many people I know use MMS on an almost daily basis, not everybody has email on their phone, and sometimes people just want to send a picture straight away. It's a lot simply than emailing because you can guarantee they get it as of that moment, rather than relying on them checking their email later.
But as I said, maybe in the US it isnt all that popular. Just like in the US, the majority use AIM, whereas in the UK, no-one does, its all MSN.