I recently read that some German dictionaries list the genitive case ending for an entry but no explanation was given as to why some publishers choose to do this. Anyone happen to know?
The genitive singular ending, together with gender and plural ending, provide strong, often definite information about all inflections of the noun.
Although there are four cases and two numbers, German nouns have at most four different forms. For masculine and neuter nouns, genitive singular (“strong” -(e)s or “weak” -(e)n) is almost always different from nominative singular, while accusative singular and dative singular are usually the same as nominative singular and sometimes (if “weak”) the same as genitive singular. Rarely, “strong” dative singular (-e) may deviate from accusative singular nowadays.
Nominative plural, accusative plural and genitive plural are always the same form and, unless they already end in -n (or -s), dative plural is different by adding -(e)n.
The genitive (and possibly the plural) is added to give a first idea of the declination, which applies. Typically an abbreviation of the declination follows, so the other cases can also be looked up. But since this is mostly found in an appendix with some knowledge of the genitive the cross-reference is not necessary.