Creepy as fuck
My aunt, who is an anthropologist, tells me it has to do with affluence and class.
In the days when Western Europe and America were mostly agrarian, tans were seen as "low-class" and fair skin was coveted. Paleness was a sign you could stay inside and have someone else do the work.
It switched during the industrial revolution. At that point socially degraded labor moved indoors, to factories. People also began to take more jobs in offices and retail. Only the wealthy could afford enough time outdoors to change their skin color. They got their tans on the Riviera. Soon the middle class copied the look. A tan became something that demonstrated you were wealthy enough to take a vacation.
I don't believe this was conscious and deliberate for most tanners. They simply copying what their peers and the people they admired did.
From my own experience, love of tanning peaked in the US in the 1970s and 1980s, when many people began to realize how damaging it can be.
Slide show: Sun damage