Is it really, though? Aside from RequireJS's subjectively awful syntax (I have built a few non-trivial applications with it, and find it generally very noisy) - it simply does not do many of the very useful things that Browserify does. Browserify is much more than just a simple dependency management toolkit, it allows you to easily write node-style code and use npm dependencies in the browser. It's practically apples and oranges.
