This is a footgun I found at a few Amazon internal apps recently. I was able to clear away probably 3/4 uses of useEffect--some of which I was guilty of adding.

Given how common this error is, there is definitely an unmet need. What people want is a listener, ie.: - recalculate a var whenever a prop changes (this is what useMemo is for) - trigger a function when a state changes (should be moved to the function that changed the state)