[micampe]

Because lossless rotation is fairly expensive computationally so digital cameras have been leaving that job to a computer.

[jstanley]

I was assuming the rotation tag only expressed axis-aligned rotation, in which case lossless rotation is not that expensive compared to taking the photo in the first place.

[jonknee]

In this case the camera is a computer though. A computer that knows its orientation.

[CountHackulus]

Not to mention that it's rotating by +-90 or 180 degrees, which is a whole lot faster than an arbitrary rotation.