"[Planetary Society's Casey] Dreier cautions that the latest glimpse of potential Trump space policy may be just that--a peek into the internal debate over NASA's mission, rather than a clear roadmap for the space agency's future. ... Human spaceflight programs are expensive, and risk overshadowing such projects. "Science always tends to suffer when human spaceflight programs go over budget," Dreier says."
Keith's note: Of course Casey Drier omits the flip side of this statement - when space science missions go over budget (crashing Mars probes in the 90s, James Webb Space Telescope, Mars Science Laboratory, Mars 2020 rover etc.) Space Science tends to suffer much, much more - and it is self-inflicted.