Hmm....that is a very good question.
From Wikipedia:
Pocky can be found in dozens of varieties. The most popular flavors include chocolate, strawberry, and almond. Some of the more unusual flavors include the seasonal flavors of honey (spring) and kiwifruit mango (summer).
There is also the bittersweet version of chocolate Pocky called Men's Pocky. There are also regional flavors of Pocky such as grape (Nagano), yubari melon (Hokkaido), giant mikan (lemony, sold in Kyūshū), powdered tea azuki bean (Kyoto), Kobe wine (Kobe). There are also such flavors as banana, coffee, caramel, marble royal milk tea, melon, milk, cream cheese, berry, sweet potato, coconut, almond crush, pineapple, pumpkin, pizza and hazelnut.
Some other unique Pocky flavors include kurogama (black sesame), kinako (soy bean flour), and green tea, which are popular Asian cuisine items cleverly incorporated into dessert flavours.
Special variations of Pocky include Decorer Pocky (which features extra decorative icing) and Mousse Pocky (which features extra thick, mousse-like icing).
A related product is Pretz, which is a savoury version of Pocky that features flavours like tomato and salad.
So I guess it's just dark chocolate instead of regulate milk chocolate. Good riddence, they can have it.