AgeLikeWine is right - tanned skin became associated with leisure and money in the 60s and 70s when commercial travel made it possible for people to go abroad. It was a signal of having money.
Conversely in the 19th century - aristocratic women carried parasols and wore gloves when out in the sun to maintain their pale skin.
This was because tanned skin was associated with the peasants out in the fields. Therefore dark skin was associated with the lower classes and pale skin was associated with the upper ranks.
Luckily for them 19th century women didn't have to go on the beach in a bikini!!!
Personally I think tanned skin looks great - unfortunately I'm a typical English rose.