Because in the end, other manufacturers are doing the same thing with just one sensor, and we’re not sure if the extra resources that have been invested in the Duo Camera were worth it. In any case, the main camera still offers a 20 megapixel sensor like the one in the One M9, and the front camera has a 4 MP sensor for some nice selfie shots.
Tests of the camera have been more or less good, but there are some claims that the picture quality could be better for this configuration. Subjects should always be captured in a clear, well-lit environment of course.
It’s also worth noting that the UI of the camera app has been redesigned a bit, and it’s now cleaner and more intuitive, giving the user faster access to more settings. A panorama shot can be taken by just swiping the viewfinder or tapping a button on the bottom right, and people can use Photo Booth and Split Capture as well.
Other camera settings are available in the overflow menu and this keeps the overall presentation nice and tidy, allowing users to focus on the features that they are actually using most often. HTC have done a good job revising their camera interface, and if the device offered a little more as a whole, it could have been perfect.