[LorenPechtel]

Cultural expectations on tanning come down to signs of wealth.

Industrialized societies most work is performed indoors, most people only tan during leisure time. Thus a tan is an indication of having leisure time and is looked upon positively.

Societies that are not industrialized most work is performed outdoors, leisure is generally indoors. Thus the absence of a tan is an indication of wealth and is looked upon positively.

Note that this lags behind reality, many places have industrialized but their perception of tans is still negative. My wife is Chinese and I sometimes joke that she's half-vampire because of how sun-avoidant she is.