Because
A) It's not well known outside of Japan
and
B) A good degree of anime fans don't appreciate intelligent anime. They want gun, sword, and fist fights every episode. COTS appeals to hardcore Science Fiction fans.
Anyways, go to
www.Crestofthestars.com they have a section for both COTS and BOTS where you can access a lot of stuff. If you wait, I can give you the URL for a sight called Daiseki, which is a fan page with lots of stuff, but I don't think it has episode lists. I've found episode lists before, but never remembered the URL's. I remember that the last episode in BOTS II is "Tears of an Abriel."