>new language construct

This was added to the language 10 years ago. So while it's "newer" than a plain old for-loop, it's definitely not "new". It was designed to work with Symbol.iterator. This is the mechanism whereby one can iterate anything that implements the Symbol.iterator interface.

As far as why folks won't just do simple for-loops, it's the same reasining every language tends to implement a "foreach", because there are annoying off-by-one errors lurking in the < vs <=. Of course one could argue that developers should be smart enough to handle this. But that's an argument even older than for-loops.