Why can't I do cumulative edits, like in iPhoto 6?

Question

I've just bought a new iMac (Core i5) running the latest iPhoto (9). It has some useful improvements over iPhoto 6 which was the previous version I used, but one thing has gone - I can't do cumulative edits any more.
In v6, I could sharpen a soft picture 100% then navigate away so iPhoto saved my edit. Then I could go back into that photograph, click Edit again, and all the sliders would be reset to their default zero settings. I could then add more sharpening to the picture, get iPhoto to save it, return if necessary, sharpen more, and so on. This was a godsend where an edit needed to applied more than once.
Now, I can't do that any more. When iPhoto saves my edit and I go back into that photo, the sliders are where I left them!!!! I can't ever apply more than 100% sharpening to a picture. That *****, really bad.
Why did they change that? It seems so unnecessary. The Revert to Original was always there, and it still is - so why can't I apply cumulative edits now?

Answer 1

Keith Barkley wrote:
But this allows you to unsharpen without having to go back to scratch.
It is not a question of treating you like a grownup, it is a question of preventing JPEG artifacts.  In the old way, you had to continually re-JPEG the image, losing quality and detail with each editing pass.  Now it always starts fresh with the master.
But I am not the engineer, so I don't know if this was a conscious choice or a result of CoreImage.
I don't ever want to unsharpen (i.e. blur). And even if I did, that was possible pre-iPhoto9 by sliding the slider into the negative band from its midway position. It's extremely difficult to oversharpen in iPhoto, even cumulatively, as the control (IMO) is usually superior to Adobe's.
I found iPhoto 6 (and now iPhoto 9) had subtle, but high quality edit controls. The chances of JPEG artefacts - at any rate from a keen amateur photographer like me - were around zero.
I believe that what I wanted could have been implemented with a simple Preferences choice :
O  Maintain edit slider positions even after Save (non-destructive editing)
O  Reset edit sliders to default positions after Save (destructive editing)
That would have made everyone happy. Now, for those pictures which need cumulative sharpening (admittedly, a small number), I may as well do everything in Elements.