We use zero cookies on our website, so we have no consent banner. But people got so used to seeing "cookie consent banners", that we are considering introducing a "no cookies here" banner.
In most cases sites could just use necessary tracking without permission but seek explicit opt-in for the rest. They won't do it that way of course because most people won't op-in unless nagged or conned into doing so.
(the other reason for consent questions where they are not really needed is people playing safe lest they have to defend the lack of a consent form in legal court or the court of public outrage)