Rob-ART offers some humorous solutions.
We’re having some fun at Apple’s expense but, seriously, why did Apple drop this very popular feature from the 2010 MacBook Air?
It’s a good question. Notably, they also dropped the IR port and the sleep LED. (It also lacks the useful-more-often-than-you-think row of green LEDs and button to display the battery level, but so did the old Air.)
The sleep LED could have been dropped because the new suspend-to-disk mode would have made it inconsistent (assuming it’d be off to conserve power), and the IR port could have been dropped because very few people used it on a very small laptop that’s often not someone’s only computer.
But I doubt that the backlit keyboard was dropped for power or cost reasons (at least, I hope it wasn’t). A more likely explanation might be that it was simply too thick.