The reason for all the discussion over the years is that a single line lambda doesn't cover 90% of the cases. If you think in terms of callbacks, I bet one liner cover less than 10% of the cases.
Whilst this is more pythonic I personally prefer Javascripts use of lambdas as more than a means of expression. More like a way of life for the language :-) And that is IMHO what makes it functionally closer to Scheme. Just looking at the way one defines lambdas in Javascript and their use throughout the language is a thing of beauty.
