I've always wondered this. Most of the major of the apostles tend to have human guards/soldiers working for them. Wouldn't it make more sense to have apostle underlings serving them, since they would obviously be more stronger? Also, in the manga we're shown that apostles are bloodthirsty and have no respect for life, yet they don't seem to be very threatening to those working under them (unless it's Wyald, who was obviously crazy). Even Rochine turned her bodyguards into pseudo-apostles, rather than killing them outright once she turned into an apostle.