I always wondered why ON 17 (Trans Canada main route) was never ON 1. It would be nice for the whole country to assign the Trans Canada as such.
Because
1. that route was Highway 17 long before the TCH was ever routed onto it
2. The TCH route is a non-entity in this province. Even in areas where it's the dominant route, it's not referred to as such. The only reason it's signed at all is to provide continuity, not because anyone really cares about it.