Cadia. The epitome of the Imperium's military might, steadfastly defending against the filth that spews from the Eye of Terror for most of the Imperium's history. Every person born on it's soil will serve as a soldier in some capacity and even the civilians are well drilled. The Cadians are a tough breed, sturdy and resolute in their task, unflinching even in the face of certain death.
Which then begs the question.... With such a strong populace trained, from childhood, for war, why hasn't an Astartes Chapter been founded/stationed there permanently?
I know there's a group of (10?) Chapters specifically dotted around the extremes of the EoT but why isn't Cadia itself host to a Chapter?