The purpose of the RFC is to simplify security on the Internet, make such decisions transparent, and to preserve clear separation of concerns between the layers. As such, the evil bit is supposed to be the only thing that a conforming device checks.
Otherwise, we're back to square 1, where you don't know what caused your packets to be dropped even though they are clearly and explicitly not evil!
Otherwise, we're back to square 1, where you don't know what caused your packets to be dropped even though they are clearly and explicitly not evil!