>>96538671
What do you mean "why"? Do you know how any of this works? Like, at all? Do you understand why the different regiments in the lor are called "the Cadians", "Catachan", "Krieg" etc.? Those are the names of the world those regiments are raised from.

Each planet above a certain population has to meet a tithe, a number of regiments they have to raise when called upon to do so. When the Imperial Navy shows up, those regiments need to be ready to go. That's the system. The famous planets are famous because they have very high standards for the guys they send. But that is in no way universal. Different planets do it differently.