They come in many different shapes, sizes, and degrees of doneness, but everyone gets one. With a casserole, you get it served just the way the cook decides it should be. There is no choice involved, except of course, whether you choose to partake, how much you choose, and whether you clean your plate. Not so with a baked potato. A baked potato is full of choices and it is completely individualized beyond the simple fact that everybody can have one.
Some people like to mash it all down first.
Others like one lengthwise cut. Still others cut it in chunks. I suppose one could even leave it whole. After it is ready, each person gets to choose how to top it. I like lots of sour cream.