Image processing has always been a necessary part of photography.
In film times this happened in dark rooms.
Today this is usually done on computers.
Retouching is especially important in fashion and beauty photography,
to show the model and the outfit perfectly.
If you don't pay attention, models quickly look like dolls and fabrics look like plastic,
eyes loose their shine or glow too much,
skin becomes structureless or appears old.
The picture should look perfect and not retouched at the same time.