From a Doylist perspective, Usagi's clumsiness is so that all of us 13 year old Japanese girls can personally identify with her struggles. Maybe she's a superhero, but she has to deal with the same awkwardness as the rest of us. Also, slapstick.
From the Watsonian side, maybe one can just turn it around? A part of her power that reminds that she is like everyone else, and makes mistakes. Possibly a nod that purity is not perfection. Or maybe she's just a 13 year old in a growth spurt. But I always come back to the memo from her future self which is written entirely in kana that dumps responsibility for raising her child on her past self. There were reasons for that, but it still seems likely that her future self might still be a clumsy goofball.
-- ∇×V
From the Watsonian side, maybe one can just turn it around? A part of her power that reminds that she is like everyone else, and makes mistakes. Possibly a nod that purity is not perfection. Or maybe she's just a 13 year old in a growth spurt. But I always come back to the memo from her future self which is written entirely in kana that dumps responsibility for raising her child on her past self. There were reasons for that, but it still seems likely that her future self might still be a clumsy goofball.
-- ∇×V