When I flew for a living it was company policy, written into the Ops Manual, that you did not cancel IFR, you flew the procedure every time, even in CAVOK. That was based on a long history of people changing their plans at the last minute and CFITing as a result, or making an approach to the wrong runway, or even street lights (the literature is full of such incidents.)
What a wonderful argument against the proposed EIR!