[@vancexentan]

You can just say that they are barricading somewhere instead of having to drag them around, or be brain dead homunculii kept on someone's basement, if you want to kept this line of thought. Technically, there isn't even any rule that forces a Master to be on the same place as the Servant, so they are skippable as far as the narrative goes. The true stars (and the reason why the vast majority of the public likes Fate) are always the Servants front and foremost.