they are useful as a guide so u dont have to be switching between the diferent ortographic views

I use them too because if the reference photos arent completely right placed, or well drawed i can do that to define the shape, so

i dont have to think too much when im modeling, and i just use the single reference of the curves (u can see them direcly in the 3d space and dont have to model in ortographic view)

if i have i doubt just follow the shape of the curves i have modelled before, they are the judge

because if i have doubts modeling them my mind gets scratched, and i hate that