Reducing Balance Depreciation ...

The only thing that changes is how to calculate the depreciation ... the rate, which is always given, is applied to the carrying-value rather than the historical cost ... except in the first reporting period when the rate is applied to the historical cost as well.

Using reducing balance depreciation means periodic depreciation expense decreases each reporting period.  Why?  This is important.  Because it is assumed that NCA is contributing less to revenue over which each new reporting period hence the depreciation expense should match that declining revenue to better match the revenue generated by the NCA to its depreciation expense.  MATCH, MATCH, MATCH, MATCH, MATCH.  That is a word that examiners like in this context.  Matching the revenue generated by the NCA to its depreciation expense to provide stakeholders with more relevant information for the reporting period.