In Canada, it is required to demonstrate some limited instrument flying skills to earn a night rating. That's because of the risk of blundering into IMC at night (particularly in falling snow). But, without an IR, there are no flight in IMC privileges. As Sam points out, there are many occasions where night flying is effectively flight without reference to the surface, even thought there is visibility. Night operations from my home runway are no visual reference within 200 feet of the surface, instruments only, until I'm high enough to see lights miles away. Serious instrument flying discipline is required even thought the privilege is not granted.