Rotating a mobile device has unpredictable effects: Depending on OS and app rotating the device can have no effect, or it lays out the content to the new screen orientation, potentially showing a very different interface or different elements, or scrolling to a different part of the content.
From my personal experience, I find that I barely ever rotate the device to "access" the different viewport layout. However, on a daily basis I struggle with apps that react to the rotation change. Often this is caused by accidentially tilting the device, or sometimes I'd even just like to hang out on the couch but am forced to hold the device in ackward position to get the desired orientation.
What are the reasons for not allowing users to disable or lock the device rotation in the device OS or app settings? Does the gain from allowing responsive layouts outweigh the negative user experience of forced rotation change?
As a little background: Amongst other advantages from building a dedicated app instead of a mobile website, I find this control over viewport orientation particularly compelling. As far as I know there is no way to control the orientation change from a mobile website, however, some applications are simply designed for only one viewport layout. My question thus is merely to figure out what are the reasons for not offering this kind of setting.