You can experience goosebumps anywhere on the surface of your body. There are some parts of your body that won't make it look very obvious for you to see. Goosebumps appearance and how big the size of the bumps will look are not dependent on the level of cold or how emotional you might be feeling. What causes goosebumps is the contraction of the muscles that are connected to the hair follicles, causing a kind of depression on the skin.
The nature of the depression formed will dictate how obvious the goosebumps will look. What determines the size of the nature of the depression is the distance between two hair follicles. If there is a little distance, the goosebumps will come out big, and it will be noticed. The reason why you don't notice goosebumps on your head is that there is no gap between the hair follicles, so there won't be enough space for the depression to be formed.