This, in combination with what you mentioned below about the rules needing to be applied consistently otherwise people get upset, is where i think a lot of editors come from nowadays someone somewhere said no previously published work and outlined what that meant, and so everyone followed suit to make things seem fair. so even in the sphere where small prints ( like Last Leaves ) are currently unable to pay for work ( which we hope we can in some way in the future ), we still abide by the "previously unpublished" standard and what that was said to look like before we came along