It's always been puzzling to me that recipes for sourdough starters begin with a series of steps that typically include, at some point, throwing away half of the mix.  That doesn't make sense to me and, I admit, I've never complied with that direction.  My starters develop nicely and I haven't found any reason to believe that my maintaining the full batch generates any difficulty whatsoever.  So, my question to those of you with a lot of exprience on this subjet, "why am I supposed to throw away half of my starter mix during its initial development?"