Only place I can see for disc brakes is in deep mud; and sandy conditions - which will cause unbelievably fast rim wear with rim brakes.
FWIW, last Winters Cyclocross World Championship race , in L'Ville KY
the racers running disc brakes found the pads did not even last an Hour.. the length of the race.
they flew in some custom made discs without holes in the edges to see if they wouldn't carry so much sand in the holes
and take out the brake pad surface as fast.
I think the 1st 10 places were all using cantilever brakes , that day.