Why do things not directly translate properly?

Translation or transliteration, gives the meanings/ideas behind the words, not necessarily the words themselves as though they were standing independent of each other. Words take on different meanings or inferences based on their position and the inflection used when the words are said or spoken. Only a human interpreter (not translator, per se) is aware of those subtle nuances, something a hard-wired dictionary-based translator, is years if not decades, away from comprehending.