Natural vs. Aquired color

In recent discussion on skin tone, I have been forced to consider a very confusing reality about the meaning of skin tone. Aside from the simply asking the question, I don't know how to address this.

Why is has it been considered less desirable to be born really dark but yet everyone works on their tan to get dark?

I have been thinking about conversations on skin whitening cream and the idea of not having kids darker than yourself-- but why does it matter?

There seems to be a fine line on when being "dark" becomes an object of qualification/classification. There is the white/"pink", there is olive-skin, light skinned dark, and dark-- and several colors in between. There is also a clear distinction between one who has acquired color and one who was born with color.

When I look through a magazine and see all the ideal models, very few are the pastey pure white that is associated with the "ideal" race. Is physically being white actually beautiful? or is just socially identifying as white that brings this idea of superiority/beauty? If this is about social classification, this would imply that the more important part is the shared history rather than the physical classification...