I have noticed a few VJ'ers that have filled out both I-130 and I-129F applications at the same time. One is a petition for an immigrant relative (spouse, I suppose) and the other is for a fiance(e). So separate fees and paperwork for the same person. Can someone please explain why it would be done this way? Thanks

I-129F can be used for petitioning for a K-1 (fiance(e)) or if filed in conjunction with an I-130 it is used for K-3 (spouse)