In my opinion it's likely to do with the fact that it's not Sam as Nova, but Sam as Sam (Formerly Nova). It's not Sam doing Nova things, it's Sam wishing he were doing Nova things and getting blueballed because he can't do Nova things.
Not only that, but it's all happening in the "Champions" book, where he has historically not been one of the lead characters. As far as I can recall, it's primarily been about Kamala, Miles, or Viv. Pretty sure Sam's only had as much screentime as Chulk.