combat roles really revolves around fear of their capture -- and, today, for the potential of rape and the resultant publicity / IO aspects. The rationale was that those in rocket and missile units would be further in the rear in a linear war and thus less subject to potential capture while the tube Arty folks were right up front. Same principle held for the aviators; initially they were restricted to transports and such, theoretically less subject to enemy downing -- despite the fact that the average female has some advantages over average males in aerial combat.

We still put a lot of stock in 1917...