Hair growth around the nipples starts after puberty. It is controlled by the sex hormones. The amount of hair that different people have is different. There are many reasons for this.
The number of hair follicles present in a particular area is different for different people. The amount of hormones in the body is different. The sensitivity of the hair follicles to these hormones is different.
So having hair on the breasts and not having hair are both normal. There is nothing abnormal about having hair on the breasts.