Complex sentence: The use of these nouns are needed in English because they bare the only case, gender and number information of the noun and the adjective that is modifying that noun does carry that information.
Split into simpler sentences: The use of these nouns are needed in English because they bare information about case, gender and number of the noun and the adjective modifying the noun does not. In English the adjective that is modifying that noun does carry that information.