Webpack does not glob-search against the filesystem like grunt/gulp/brunch/broccoli/make. If you look for that: Sorry, webpack does not "replace" simple tools like that.
Think of it as a tool executing require.extensions at build time. It's not operating on files as much as it's looking directly at the source-code AST. That makes it more complex to get into over the glob tools but it's worth it.
It's also just as modular as anything else: http://npmsearch.com/?q=loader%20AND%20keywords:webpack
I really hate systems that are built like that. Nobody should build software like that.
I just want simple tools with a clear API that I can combine together and easily replace by other tools, like in the Unix tradition.
I guess it is a case of "LEGO versus Playmobil". The former allows modularity, while the latter is just complex crap that allows you to do nothing other than what the instructions say.