the thing is i've seen some Asian shows and street scouting is a thing and it's mostly minor who are scouted so i am not 100% sure it's a shojo manga thing (although i would find that creepy too if someone approach me suddenly) , obviously there is the thing with eating disorder etc but i guess in this case the ML really had no purpose in life and he hated himself and his looks which doesn't fit in so if this modeling thing can finally give him some purpose then i could see why his adoptive parents were ok with it , I guess this is one of the rare cases were the choices were logical and support the characters