Why couldn't one single dichotomous key be used for all of the organisms on earth answer

in the poem young by anne sexton and in the poem hanging fire by audre lorde, they both talk about being alone in their childhood. in young it talks about how she lived in a big house with 4 garages and how she layed in the grass at night. in hanging fire it talks about how she didnt like her body how she was scared she was going to die and her mom would be in the room with the door closed and she talks about how she had to learn to dance for the next party and how her room was too small. she also talks about (hanging fire) how she was alone and abanded and how people never toke her side and see how she truly feels about the world around her. in both poems they talk about when they were younger. both poems explain the side of a happy alone rich girls life in young and in hanging fire it talks about a girls who is poor and doesnt like her body..