I think that one of the main problems with the Tongariro Crossing is that there are not a lot of similar hikes (in NZ we say "tramps" and "tramping" for "hikes

I think that one of the main problems with the Tongariro Crossing is that there are not a lot of similar hikes (in NZ we say "tramps" and "tramping" for "hikes and "hiking") that attract tourists, so if you're not heading to the South Island it's your only real choice for this sort of trip.