Why we don't delete fetcher data when fetcher key change?

[CurryYangxx]

I am reading the source code. In useFetcher hook, we have some clean up logic. Every time the fetcher key change, we will delete the fetcher from router state. But the fetcher data is retained in fetcherData.
I want to ask why we don't delete the data from fetcher data?

react-router/packages/react-router-dom/index.tsx

Line 1711 in 0f2b167

router.deleteFetcher(fetcherKey);

react-router/packages/router/router.ts

Line 2903 in 0f2b167

function deleteFetcher(key: string): void {