It is useful to generate a midplane perpendicular to the line connecting two points. Especially for neurosurgeons.
Users only need to place two points to get the mirror plane of these two points
Instead of changing slice orientation, it is more common in neuroimaging to transform the image into a standard coordinate system that is aligned with axes of the brain.
You can do this in Slicer for example by using ACPC transform module. It aligns the brain in a standard orientation based on the AC-PC line and points in the midsagittal plane.