multitouch, what for?

Multitouch works fine and good in mac image preview app. I can rotate and zoom pretty comfortably. Though rotate is a bit too flexible, but still works fine.

Now, I have a huge chart and was looking forward to zooming to deeper levels of clarity. The preview was not able to provide a wider view so I thought its better to go fullscreen and than zoom. Exactly the context in which multitouch zoom would be an awesome feature and exactly the context in which preview says no to multitouch.

Its hard to find a reason behind this interaction model.

Makes little sense to look at this big chart in full screen when I cant zoom-pan: