[@Jarl Coolgruuf]

Good question, the origins of M.A/I.D stem back far into the past (over three thousand years actually and that was long before they would ever be known as what they are now). For most of their history they operated more-so as assassins and information gatherers. This was because women would usually not be registered/expected to be a threat - let alone one bound in servitude. 

Without getting into much spoilers, the Shadow Queen is an outside force that initiated a bloody civil war within the organization (which had no formalized name at the time). This conflict was actually fought mostly by men. This occurred around 2 B.C and then her (and the remaining female servants) largely went unaccounted for up until the year 1111 A.D when Henry the Fifth was crowned the Holy Roman Emperor and somehow, someway, the Shadow Queen found her way into his presence and saw her female servants employed by him (which made them loyal to the English Crown up until after WW2 where alleged reports of them defecting to the Nazis exist). 

That might just seemed like an explanation for a whole lot of nothing. What I am trying to get across is that the Shadow Queen has always employed females for hundreds and hundreds of years. She is a traditionalist who believes that women are to be housekeepers and care for children. However, she also believes that women under the guise of loyalty and control can also be very dangerous and serve to further her own agenda.

The current group of M.A/I.D are by far the most combat trained and ready individuals in the history of the organization. Previously, they were about 10% assassin and spy with the rest being domestic servants. The Shadow Queen believes women make the best domestic servants, but is also turning them to a more combative role because the final phase of her plan is about to begin due to the technology being ready.

Just to sum up that mess of text - it is that way because the Shadow Queen has "traditional values."