* Facts
It gives the players a voice.
* Speculation
We may be forced to use magic, as part of the main quest.
It may be used as a cheap way to get out of tough situations. (Make future dragon fights easy, etc. Yeah, I know, don't use it.)
It looks like the control passes through our hands as we absorb the dragon's soul.
Feel free to explain your choice. I'm curious to see if I'm in minority conserning this.