I found that a few cigars I left in the bottom of my humidor over a year and a half without rotation had flattened on one side from the weight of the other cigars on top of them. Has anyone else seen this problem or was it just because these particular sticks were lower quality? That would be a good reason to rotate regularly if nothing else, unless maybe your whole humidor is filled with box pressed.
As for the uneven burn issue, like others have said, I resolved that issue for myself by rotating the cigar as I smoke it. I think it's because when you're drawing on it, either the shape of your mouth and tongue or the angle of the cigar causes more airflow on the bottom half of the cigar which makes it burn a little faster than the top. Occasional rotation easily evens it out.