When you develop a web app in Rails and you hit a snag you can usually solve it by grabbing a Gem or a Rails plugin. Similarly, if you need to do something in Java there is most likely a good mature library out there already, and you can just drop a Jarfile in your project and go.

I'm talking about all the odd little things you end up doing in web apps, like drawing charts or parsing PDFs or talking to some obscure web service. You'd be left to solve these things on your own with Smalltalk (although solving them may be easier).