Approval voting fails in a situation that is pretty common in Europe (e.g. French presidential elections) - you have center left, center right, far left and far right candidate. If you vote for center left/right, you have to decide whether to also approve center right/left candidate, which may be contrary to your values, corrupt and incompetent, but at least not communist or fascist. That is why later-no-harm property of IRV is important.