I don't currently blanket, but my two don't need it either. When I first bought Lily, I almost blanketed her for the winter. She came from KY and is more of a thin skinned pony. We were having a really rough fall; windy, cold, and rainy and she was really miserable. Thankfully, while I was looking for a blanket that would actually fit her she adjusted to the weather and actually grew a coat. I'm sure it helped that she had good shelter, a ton of hay, and grain supplement. Now she grows a good coat on the same schedule as my QH and is happy as a clam all winter. I think sometimes we jump the gun on using blankets on a horse that doesn't grow much of a coat.
IF I had a horse that needed it I would blanket, but I'm glad I don't, my lifestyle and budget really requires me to own horses that not hard/difficult keepers.
I think some people overdo it, but I'm sure there are plenty of people that think I underdo it, as long as the horses are not suffering (and I don't count a day or two of discomfort here and there as suffering) I keep my thoughts to myself.