I have both mocked and championed session zeros in the past. They’re really being held up as this important thing that needs to be done, but can often be ignored if you’re in a familiar group. You might have already learned all the pertinent session one details over time: what types of story they like, and what they dislike; what they find fun, and what is unfun or disrupts their fun. Having played with most of my group for a decade, this discussion can be skipped or streamlined into a short convo at the start of the session.

Unless you’re doing a new genre of story and want to get the tone right.

If you’re trying a new style of game, it certainly behooves you to sit down and explain what type of science fiction is being played or what genre of story you plan on telling with a flexible system, like Kids on Bikes. Or even what type of superheroes one should make when planning on participating in a comic book inspired game.