I think some people are secretly yearning to play a QB who can win games and we don't have one of those on our roster, right now.
My personal opinion on why Lewis is being held back is because the coaching staff doesn't want to put him out in front of this season and set him up for failure - because that would likely impact recruiting in a very substantial way.
We don't have a QB who can win games without solid talent around him, two levels deep. The rest of the offense has some growing to do. Our run blocking is weak and our receivers are best described as "serviceable".
For this season, Kyle, Jon or Gio, it really doesn't matter. This season has never been about anything more than next season. Next season is probably 4 or 5 wins.