Most cutscenes are too long and boring. Looking Glass was the master of making cutscenes interesting and just the right length.Besides, presenting everything that happened before Citadel as a cutscene works for putting the player in a state of mind similar to the Hacker, who has just woken up from six months of cryosleep with a hazy, dissociated recall of how he got there. If you played all that in first person, you'd lose that sense of discontinuity. It would just be "I'm playing on Earth. <level load> Now I'm playing on Citadel." Bleh.
It seems they're thinking about SS2's earth.mis, which wasn't bad, if something like that is a good fit for this game is another discussion.