Zygmont Frajzyngier states that a general characteristic of case marking in AA languages is that it tends to mark roles such as genitive, dative, locative, etc. rather than the subject and object.
zˈɪɡmɔnt fɹˈædʒzɪŋiɚ stˈeɪts ðˌæɾə dʒˈɛnɚɹəl kˌæɹɪktɚɹˈɪstɪk ʌv kˈeɪs mˈɑːɹkɪŋ ɪn ˌeɪˈeɪ lˈæŋɡwɪdʒᵻz ɪz ðˌɐɾɪt tˈɛndz tə mˈɑːɹk ɹˈoʊlz sˈʌtʃ ɐz dʒˈɛnᵻtˌɪv, dˈæɾɪv, loʊkˈæɾɪv, ɛtsˈɛtɹə. ɹˈæðɚ ðɐn ðə sˈʌbdʒɛkt ænd ˈɑːbdʒɛkt.