Why do movies always have to say an obvious line to make viewers know two characters are siblings?

[Vermilioncore]

For example a scene will have the main guy talking to a girl and just so the viewers know theyre related, they’ll make one of them say for example “hey, shut up or I’ll punch like dad used to.” Or “cmon get in the car lil sis!” Like cmon no one says those things irl

 

[Alt Number 3]

The director thinks the audience is retarded