A typical TV commercial for cotton shows a multiracial group of schoolchildren holding hands while crossing a street, accompanied by a warm voice-over message about learning a lesson that we "won't get anywhere at all, unless we all get there together."  Since this obviously has nothing to do with the properties of yard goods, the communication cannot meaningfully be analyzed any other way than through its symbolism.

There is admittedly an element of risk in explicating such messages, akin to that of an art critic deciphering themes in abstract painting, because there is no way to objectively and conclusively prove what's being conveyed.  Still, with that risk acknowledged, it is more than reasonable to note certain salient points.

Certainly one thing the cotton commercial is saying, in symbolic terms, is that cotton is to be associated with "nice" people—people who are high-minded, and so forth.  Why would a commercial want to do that?

Well, to begin with, most people probably want to think of themselves as nice. 

But perhaps more to the point, in our culture there are certain underlying associations between "nice" and "well-bred" and "affluent" and "high-status."

What this commercial appears to be doing is putting across a symbolic message that cotton is the choice of "the better sort of people," clearly differentiating its wearer from the vulgar rabble in their polyester.

That's something you could never say directly nowadays, without sounding materialistically elitist, and thereby losing a lot of people whose values include things like vegetarianism and "living lightly on the earth," who happen to constitute a significant portion of the market for natural fabrics. 

By saying it symbolically, a marketer can convey the same message without generating objections, and end up with a lot of people strangely wanting the product, without being quite sure why.