Someone will probably get mad at me for saying this, but the reason that some people purchase night sights: Even though home defense is de facto illegal, some people plan on using their handgun for home defense should the unlikely need arise.
The elephant in the room is that a lot of Canadians own guns for self defense. They might be avid recreational shooters, belong to a shooting club, be lifelong hunters, and go all politically correct on anyone who would suggest otherwise... but deep down, maybe even only subconsciously, they recognize that a gun can be used for self-defense and prepare as such.
Tritium sights will help them shoot in the dark, such as during a home defense scenario.