I think it is to do with Newton, in this regard. Mass, as unperturbed air in front, is loath to move, "Remain at rest" (#1). Once entered the stream tube, it is loath to rest, 'momentum' (#2). Confronting the wing streamline, it must slow, "damming" the release of air through the aperture: wing, ground streamlines.
Hence the compression, increased pressure, and lift without benefit of incidence increase? (either AoA or incidence).