I can add one more advantage to clearing the spot: When tying on a new jig, if you drop it in the snow, you might as well kiss it goodbye. At least if the snow is cleared you have a better chance of finding it on the ice. I ran into this problem on pleasant a month or so ago. There was a few inches of snow on top of a few inches of slush. I didn't clear any because I didnt want to stand in an inch of water. While tying on a jig (over my box for this very reason) I looked over at my rod in the water. I no more than turned my head and by body and hands decided to follow. Of course, not holding the jig over the box anymore, I dropped it right in the snow. I tried digging for it through the snow and slush but it didn't work. Luckily, I had another jig (same style) and commenced to trying to tie it on. Well, apparently I didn't learn from my first mistake. I looked over at the Vex and I'll be damned if I didn't do the exact same thing.
Long story short, bare ice saves jigs.