Here's why Sam gets summer clips. See all that wave... you don't get wave without having some thick hair. Remember, he's 1/2 curly horse and this is his normal summer coat.
Sam's summer coat
The following is typical of a curly horse in summer (possible this horse is also a cross). Similar coat to Sam's, but shedded out mane and tail. Sam loses some mane (which is thin and brittle already) but doesn't seem to lose his tail - not all curlys do.