Interesting, etymologically.
"Good bye" is a contraction of "God be with ye (you)", which isn't quite so abrupt. "Au revoir", literally, "until (we) see again".
Similar to "Hasta manyana" (until later), or "bis später" (same), Spanish and German, or "zài jiàn" ("see (you) again", Mandarin Chinese) . Farewells (literally, "fare thee well", be well) in many languages share similar attributes.