"The black and white image was, in some essential way, photography’s defining feature – that was where its power lay and colour diminished its artfulness: paradoxically, monochrome – because it was so evidently unnatural – was what made a photograph work best." William Boyd: Sweet Caress: The Many Lives of Amory Clay
All photographs are simulacra, imitations of a reality that is filtered by a camera’s film or sensor to capture light and convert it to lines, shapes, and colors. Different film stocks and different cameras present the same reality in different ways. (Not to mention choices made by a photographer in post processing.) People generally don’t think about this, ascribing to photographs – at the ones that don’t look "doctored" – a certain level of realism.
As photographers increasingly use digital filters and presets to alter their photos, these images stray further and further from the reality that the camera captures. Perhaps a filter applies a vignette, a bit of texture, and washes out the colors, to suggest an old-fashioned image. Or a filter might increase or decrease saturation, sometimes to create a false ideal of accurate skin tones (this is what Kodachrome was designed for, at least for white people). Other filters are used to match current social media fads, rather than to enhance images in any particular way.