I do honestly believe that most of the people that are aware that a lit keyboard was offered , if polled will say they would have preferred to have it. does it really help, probably not, it may be of limited assistance, and those that never knew about it probably don't curse it's absence. It does however give a sense of completeness of a well thought out higher end product that dotted it's I's and crossed it's T's, and inspires confidence, yielding a positive consumer experience. When expectations are fufilled, brand loyalty is generated. Which generated perpetuality of the entity is ensured. It is more economical to win a customer over once, that had a positive experience, and will buy the next three products ( in my case , my daughters macbook, then my wife's i pad, now my air) than to have to try to win him over three times, as in the case my daughters chevy, my wife's honda, and my mercedes. I am generally satisfied with the benz, and will probably buy another, but the chevy and the honda didn't inspire loyalty, although i had no big problems.
So not having a lighted keyboard wasn't a deal breaker, the deal for the air was sold by windows, whom did not yeald a positive experience, or I wouldn't have looked any further than MS. Brand loyalty is a vary valuable commodity, that I think no manifacturer wants to overlook.