The purpose of scientific publication used to be to deliver useful scientific results to one's peers. This meant that everyone ran their own personal filter of which peers were working on interesting things, and which collections (journals) were reproducing the most interesting ones. This system still works relatively well for most conscientious researchers. The idea that we should also use publication metrics to rank researchers was never part of this system, and it obviously leads to all sorts of spam (that most scientists just work around) but that seems to really upset non-scientists.