They may not look nice, Turtle, but they sure keep the girls from ruining the studio floor when they wear through the OEM heel tip and expose the nail...
For me, the big reason why I wear heel protectors it to prevent uneven wear on the heel. I tend to roll toward the outside and if I didn't put the suede crosses on the bottoms of the shoes I'd wear off a noticable amount of the outside edge of heel in just one practice session. The uneven wear then makes my tendency to roll outside even worse, compounding the situation on future wearings. The exact same thing happens with plastic heel protectors, but if I use the suede ones the problem goes away completely. It takes me about three or four months to wear through the suede heel protector, and my heels stay flat and even the whole time. As I learn more about using my legs properly and also strengthen the muscles of my inner legs via Pilates this problem has lessened, but the tendency is still there. It used to be so bad that one time years ago I dislocated the heel in a pair of shoes.