For most games, the evil path is only created so the player technically has a choice, so they feel like they played a role in the path they took. In reality, most of the time there is truly only one fully developed path and the developers knew which you would take.

I don’t want to call it lazy, because it isn’t and is just a smart use of resources. However, when a game actually fully fleshed out the evil path it is a work of wonder.