The way I understood it was that "the-worst-waste-of-money" (and possibly "the-most-worthy-unfunded-program" as well) is a label applied in retrospect. To fund the most worthy unfunded program, you'd need to unfund one of 100 programs. It's likely that of the 100 programs, one will turn out to be an abject failure, but it's hard to predict which one it will be ahead of time. Conversely, just because the unfunded program seems most worthy now, doesn't mean that earlier one could have predicted the need for it.