I think one key reason that paintings are attractive lies in simplicity. It must be that way. It can't go the other direction and would be impossible to make a painting more complicated than nature with all its variations in texture, color, and ever changing light. Landscape painters recreate nature but must put it in simpler terms if by no other reason than only a few colors are used on a palette compared to the millions of nuances we see in life.
It could be that intuitively a viewer likes this simplification in his or her life as does the painter. It might make things clearer in some ways and gives answers to the heart and soul that might otherwise be lost in the ever changing three dimensions.
Art is a process of transition as light and paint are completely different from each other and can only be compared in the most general sense.