Why do iPhones no longer support upside down screen?

Is there a technical reason why Apple stopped supporting upside down screen viewing? I cannot imagine that Apple would have decreased functionality on newer iPhones without a good reason. Is there something about the new iPhones that makes it a very undesirable feature?

From a purely programming perspective, this is an easy feature to implement. Why remove it if there is no good reason?

Anyone have some real technical insight into this decision?