Because it is not faith in God. It is faith in self, or something else. It is a false faith. The Caesarius of Arles quote fits there too.
As for the “Andreas” bit, I don’t know the quotee, but you seem to be misapplying him to conflate belief and faith again. Lutherans don’t do that, no matter how much you wish they did.
Why does your church do the same? Is it because Christ’s work is greater? That He, alone, might deserve all the Glory? That it might cover all our sins in their entirety? That we receive it by grace and not because of any works we ourselves do to appease a bloodthirsty god?