The constant mobilization of the adult population in as near a state of total war as can be maintained on an interstellar scale has something to do with it, I'd think. Things got real rocky for a few centuries there after imperial unification but before the age of the adult diaspora. Also there's the psychic death cultists the empress employs as her personal enforcers.

[She is... perhaps a little too matter of fact about all of this. Alternia's fucked up, yo.]