Health-
Short sleeves are way easier to be mattir then uncovered hair.
I’m not paskening, only saying that when you are analyzing the sugyas and the halacha it is much easier to be melamed zchus on those who wear short sleeves, pants, etc. than those who wear their hair uncovered.
I am actually curious to know if you can find me one clear source in the gemara and rishonim that any dress code is required, apart from not dressing in a markedly provocative manner.