UseMemo should not be used for fetching/kicking off a fetch either. UseMemo fans should be pure. Using logic that belongs into useEffect (logic that happens _outside_ the reactive flow) could potentially lead to other side effects which are very hard to debug. Just a example: a lot of fetch implementations are using fetch with a cache triggered in useMemo returning immediately. You will probably have a setState somewhere in the flow which will terribly interrupt react and break your page.

In case you trigger a native fetch, you've got no way to cancel the call due to the missing cleanup fn.