I like rectangular tees. To me, their form fits what they are: artificial. In fact, clearly artificial — dead flat expanses on land that presumably wasn't that way to start.
Of course, much of golf course construction is artificial, intended to look natural. But tees aren't intended to look natural; they're intended to be unnaturally flat. So why even pretend that they're "natural", undulating, curvy, etc.?
Besides, there's a certain poetry to it. There are two linear shapes on each hole: the man-made tee, where you start, and the man-made flag, where you finish. You start and end at orderly locations; in between, everything is "wild." It's a journey. I feel it...is this making sense to anyone?