When Java was introduced many text editors did not support unicode directly. Escapes allows you to use unicode identifiers with an ascii-only editor. You probably wouldnt want to define you own non-ascii identfiers, but a third-party library might have them.
You can escape identifiers in JS, too. But what you can't do is escape just _any_ source character like the way it's defined in Java and used in the example. Writing `foo = \u0022bar\u0022`, for example, is invalid.
