Actually, for gravel-type riding, I think suspension IS more about comfort than traction. At least on the gravel I end up riding, traction is taken care of by tire pressure. The bumps are just not large enough for suspension to play much of a role in that. I think suspension is mainly needed when people still want to run smaller tires and high pressure.
And in terms of comfort, the rear is more important to me on gravel riding. I don’t have any suspension on my gravel bike. However, I have considered getting a (very short travel) suspension seat post. I have never once considered getting anything for the front.
Mtb is very different, IMO. The terrain is usually bumpy enough that suspension is needed to maintain traction and control. Therefore I find it more important in the front. Also, despite my wanting a suspension post for my gravel bike, I have not found them very useful on a mountain bike.