1. Maybe it's not as easy as you think. 2. The MMS system isn't as anonymous as the Internet and someone didn't want to burn an identity making this worm. 3.

1. Maybe it's not as easy as you think. 2. The MMS system isn't as anonymous as the Internet and someone didn't want to burn an identity making this worm. 3. A combination of 1 and 2, where the people with technical skill to do this would only use it on specific targets.