Sketch Plane auto-orientation....

When I first pick a sketch plane and start a sketch itautomatically makes the plane square on to the screen, thereafterit does not.
Can anyone explain the rationale behind this?
In SE I believe you can set the system to either rotate the modelso the plane is square on or leave it as selected for all sketchoperations.

It's not a major problem just curious.SolidworksSketching