User blog comment:The Shadow User/Squadmates in Mass Effect 3/@comment-1746153-20101013152254/@comment-3053284-20101013171414

Because you need a new Normandy to fight the Reapers. Just as SR1 wasn't advanced enough to fight the Collectors, I'm sure SR2 is not advanced enough to fight the Reapers. And it would be nice to have a new, better and larger vessel.