I recently uploaded a scanned model in an A-pose which you can see here:
This is not a sexy pose by any means, but the reason I scan in the A-pose is for animation rigging. Yes, a T-pose is preferable, but with camera rigs that can be too hard to capture. The hands are too far from the body. You would need to re-position the cameras to focus on the hands then you would have focus problems with trying to get the hand and body in the same shot. With an A-pose you can scan without changing the camera configuration. You can easily adjust rigs from Daz3D or Second Life to an A-pose or (as you can see in the video) you can quickly create a skeleton in Blender which you can use to pose your model into a T-pose so you can upload to auto-riggers such as Mixamo.
Here is a short video demonstrating the process: