Why does nouz ask for access to all orders?

Because the default order scope on Shopify only serves the last sixty days. A statement built on sixty days of history cannot show you last year's season, cannot price a product's real return rate, and cannot tell you whether this month is good.

The extended scope is read-only, like every other scope we ask for. It lets us read the whole history once, and then keep it current. It grants no ability to change anything in your store.