It's far from "completely wrong". Sure technically you are correct in that the rain sometimes might land in a place that is usable by people, but practically speaking it's nowhere near predictable or scalable enough to actually rely on, which is, once again, what is really being discussed here.

As I said in another comment, talking about farmers using rainwater for their crops:

> Rain is not predictable at the scale of a crop season. Rain is not scalable, it’s extremely localized.

> Rain happens, and when it does your crops get watered, but you can’t in any way shape or form rely on that.

So, congrats on being pedantic enough to miss the forest for the trees, I guess.