@ceilingcat - You're right that people can't anticipate every future event. Still, I feel like in a lot of instances, you can definitely anticipate enough to make a solid plan.
For example, say a store has too much stock of a product that isn't selling. They decide to put it on sale at a deep discount to get rid of it and not restock that product.
A few things could happen: they could sell all the product, or not sell very much of it. In that event, they would have to decide what to do with the remaining stock.
Yes, the store could burn down, or a flood could happen. But those two things aren't as likely as the other two things I mentioned. I feel like scenario planning is still valid even if you can't plan for every single possible outcome.