Plein air painting is a different experience than studio painting.
For the artist and the viewer...
If the artist works in a studio, they most likely work from photographs, which involves a process of transferring the 2 dimensional surface of the photograph to the 2 dimensional surface of the canvas. The artist, therefore does not transfer the atmosphere and 3rd dimension of the location, because the artist is not physically experiencing it at the time the artist is painting it.
The environment engages all of the senses to record the essence of the subject.
and not just a photographic likeness.