Culture is part of it. The Indian cast system for example has been in place long before media advertisement and the cosmetic industry came into being.
To put it simply it is the primitive cultures and beliefs that made the industries behave in such a manner.
What has caste system to do with it? Exactly how much do you even understand it?
It had tons of problems but it's not related with OP.
And no it's not primitive cultures that made this industry- Fair and Lovely is a product of Uniliver which is an Ango-Dutch company. And of course the colonial heritage of centuries is hard to get out of the system.
Funny part is that they did use their Indian subsidiary to get the the product patented back in 71 and sell this product all over the world and many think it's Indian product. India had barely gotten independence in 1947 - I doubt the research for the content of this product was done here. (Similarly Pond's too is a Unilever product though patented in USA.)
It's ads are always criticized for promoting fair as symbol of confidence and beauty while downgrading darker skin since 1971. I suppose the idea would bring more criticism if they used the main company for their patent.
BTW- there is a difference between wanting to look good and wanting to look white/European.
We don't get just tan here- when you are out in the noon in places like Allahabad temperature rises above 45 degree C and the hot winds called Lu would burn you outright. It makes skin dull not just dark. And no, most Indians do not use things like sunscreen lotions or let alone make up. So some basic skin care is necessary. The products like 'Fair and Lovely' take advantage of that too along with promoting the negative idea.