I think they would never be trusted. Clan loyalty was paramount. A man would never think of surrender or betrayal, and even if he did, he would not be trusted, because the victorious men could never imagine such a thing (like Japanese in WWII).

Secondly, there was literally no work for men to do, except fight. Another man is another mouth to feed and water. In the small scattered settled urban locations, in the few major oases, there was work (farming, building, digging irrigation channels, etc), but they had E. African slaves to do this, because they could be trusted (no hope of escape; all were castrated).