Everything as a Par 3 is just easier for keeping score. I personally don't measure how good my round was against what the course par is but against what my competitors shot, my historical scores and how I felt I played (did I miss any putts, shank a drive etc.)
The issue is that scorekeeping techniques have nothing to do with par. I use that trick too, it's easier to keep track of your strokes by counting above or below 3 on every hole. That doesn't mean that everything is par 3, there are lots of really good reasons for consistently applying a real par standard to our courses that includes par 4 and 5 holes.