Because certain things were just assumed and taken for granted in the creeds, the creeds are silent. Consequently, these so called creedal Christians believe they can deviate from the faith since the creeds are silent. The modern, best example is same sex marriage. The creeds do not mention it. It is something no one would have even disputed until the last few decades. None of the Christians participating in the great ecumenical councils of early Christendom would have even considered same-sex marriage. It did not need to be a part of a creedal statement. The Biblical view of marriage was universally accepted.