Creepy as fuck
The main reason I think people like tanning is to look like everyone else; they don't want to be the last woman (or man) standing. Also, you can wear anything with tan skin. When you are pale, certain colours just don't look as great on you as when you have a nice golden tan.
Another reason I think is to help hide skin imperfections such as acne, discolouration and even body hair....the list is basically endless. When you are pale, your skin magnifyes those things like a big red splot of paint on a fresh white canvas.
However, tanning causes long term problems such as wrinkles way too early, thick and leathery skin, aging, skin cancer and much much more.