This question comes from observing a game show called ガキの使いやあらへんで ("instant miso soup" episode), where the participants have to match a product to the one they consume while blindfolded. They are only allowed to try one product at a time from the pool of products, and they have to declare whether it is, or is not the same as the one given to them initially before being allowed to try another one.
(The other participants also similarly use ではございません and です)
By symmetry, I expected でございます to be used for "is". The symmetry I have in mind is:
ではございません ← ではありません ← ではない = だ → です・であります → でございます
It seems incongruent to me, that is to say that the use of ではございません implies the use of でございます but です is used instead.
Why is です used instead of でございます as expected from the above symmetry? Or if I may ask from the other direction, why ではございません instead of ではありません ?
My conclusion is that either my symmetry is flawed, or the social context of "declaring is" and "declaring is not" is different enough so we cannot compare using symmetry.