Agreed agreed - was thinking in terms of possible extensions. But then I saw the video just today on HS2 plans for Preston, and those bays are gone. So will need another plan!
Maybe in an even world, it could justify them on population. But given they have been so erratic in provision, I don't think they would be missed, if the core needs (Preston and Manchester, maybe Lancaster or Blackpool) - were met and compensated in place of their removal.
Bolton is a large suburban/outer town - yes it's big but not everywhere has demand for long distance services. It's unfortunately located on a loop, and historical demand will have adapted. Wigan, Preston and/or Manchester do the job heading north and south.
I wouldn't say Bolton is "on a loop" when it is literally between Manchester and Scotland!