[The Nomenclature of Territorial Units for Statistics](http://en.wikipedia.org/wiki/Nomenclature_of_Territorial_Units_for_Statistics) is an EU standard which defines three levels of territorial units. Whether directly because of this or because of related regulations, Poland underwent an administrative reform a couple of years before the EU accession. Before the reform, Poland had a two-level division, which was changed to a three-level one. 

Why is it considered better that the countries of the EU (at least the larger ones) be divided this way?