This show seems very keen on using forgetting stuff as a way of not dealing with the consequences of events. So we've killed off Rory, and wiped it from Amy's mind so that she can carry on next week as if nothing had happened. So... what was the point of him existing in the first place again? A totally inconsequential character death with little or no emotional impact at all. And how does Rory never having existed fit with the timeline of the last couple of episodes in which he played a role in the plot, and which needed to happen to get to this point?
We remember him, so does the Doctor, but Amy doesn't. That's the point.