I remember hearing in grade school that pale skin was desirable in the past as it was a sign of a life of leisure, indicating a lifestyle that did not have you working outside constantly and developing a tan. These days, however, everyone is eager to get their "summer tans" in time for the beach seasons. I was wondering at what point (or during what period of time) and for what reasons tan skin became desirable.
It's a matter of scarcity, in the same way that a big round belly used to be symbolic for riches. For many people the day to day activity was working outside, in the fields, doing things during which they became dirty, greasy, getting callus on their hands. When you could to not get dirty and afford to carry an umbrella all day to protect your skin, that was a sing that you were a well-off person. When people started to work in offices mainly, in the second quarter of the twentieth century and the pay after the initial WW2 breakdown started to increase again, people got more for leisure. This initiated more frequent traveling, increased the calories intake, and made grossly starved bodies the dream to live up to. So nowadays a healthy and natural tan, together with the right (close to zero) amount of fat has become the desire.