Why omit the final verse of the Te Deum?

Towards the end of the Te Deum, we are given the option of omiting the last verse. Why?

According to many who have researched the hymn the optional verses are parts that are believed to have been added to the original hymn later on.

As the Catholic Encyclopedia notes:

verses 22 to the end belong to a wholly different category, being taken mostly from the Psalms

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