It looks like the new thinkpads costs as much as new mac books , why would i consider thinkpads over MBA? Thanks .
If you like OSX better than Linux or Windows, it makes more sense to get a Macbook. If not, Lenovo has a better screen at a lower price than the rMBP, and at the same price as the MBA.
Judging from your other comment, you have already picked OSX. If it works better for you thats all that matters, but its silly to pretend that you can't comprehend why other OSs exist. The answer is simple, not everyone likes the same thing.
Unfortunately, I didn't have enough for a rMBP, so I ended up spending a third of the cost of a 13" rMBP on a Thinkpad so I could run a dedicated Linux machine.
That being said, if someone just happens to prefer Linux, you really can't beat a Thinkpad from the T, X or W series'.