Why does giyu skip out on hashira training?
Giyu is what you’d call a lone wolf.
Webthere are times when giyu is irresponsible, alienating from the general plan of the hashiras.
But accidentally because of such irresponsible time, he found the most important factor.
Webalongside his master sakonji urokodaki, he vowed to commit seppuku should nezuko ever consume human flesh.
Furthermore, his caring nature is the reason.