Why doesn't iPhone mail and other apps switch to landscape when you turn the phone sideways?

Not all apps are designed to be used in landscape mode, I agree some should be able to as it’d be nice to use a large keyboard in mail for instance, but they’re just not programmed to I’m afraid.

So why not – I see no technical reason for not being able to—was the landscape mode an after thought that some programers didn’t hear about? Doubt it – there has been plenty of time to add it.

I think screen real-estate could be a problem, as typing large amounts of text in landscape view can make it difficult to find where you are in the text as there’s not much room for that to be displayed when the keyboard is in use.
But for other apps landscape would be nice, even if it meant putting some controls at the ‘side’ when in landscape mode. Though Apple do like consistent design so I doubt they’d put buttons at the side instead of top and bottom.

The calculator is going to have landscape scientic mode soon. The other apps are restricted I guess due to the answer given above. I can’t see why You Tube doesn’t flip round though?

restrict space—how so you could use it in tall mode or landscape like teh rest of the apps