(If you're having lots of shedding or noticeable thinning then disregard)
Curly hair can be pretty fine, giving you the illusion that the density of it is thin. You can have thick density of curly hair, yet it still feels thin. The shaft of curly hair is like a ribbon, flat and wide, so it compresses easily. My hair is ridiculously fine, but really thick, and I used to think I had thin density, but no, it's the hair strands that are thin. It's really deceiving...lol