This may be because it has the potential to be an honest indicator of male condition, viability, and/or age.
ðɪs mˈeɪ biː bɪkˈʌz ɪt hɐz ðə pətˈɛnʃəl təbi ɐn ˈɑːnɪst ˈɪndᵻkˌeɪɾɚɹ ʌv mˈeɪl kəndˈɪʃən, vˌaɪəbˈɪlᵻɾi, ænd slˈæʃ ɔːɹ ˈeɪdʒ.