Why web frameworks tend to grow to become such unwieldy beasts?

Most of the web frameworks I know tend to do at least two things - the web stuff plus creation and initialization of all other components. This means that the framework is coupled with all of these components and this is the root of all evil in web frameworks. Of course you need a place to do that object creation and wiring work - but it is not really related to web stuff - it should have it's own place in the program, ideally in a Dependency Injection compartment, not necessarily a container based on the available libraries - but it can also be coded by hand (I might change my minde some day but for now I don't see any reasons to use DI container libraries in a dynamic language like Perl). All the arguments about using Dependency Injection apply also here, but even for someone rejecting DI it should be pretty obvious that reading config files and initializing objects is not much related to web stuff and if you buy the single responsibility principle you should split them into separate libraries.

I don't know Django or Rails too deeply - but I've observed this with Catalyst. Now, Catalyst is supposed to be decoupled from the Views or Models and other Plugins, there are many different ones in each category and you can replace them freely in your programs. But Catalyst code-base is still pretty big and then you have all these Catalyst::Models, Catalyst::Views and Catalyst::Plugins that don't really do any meaningful work - they only map one interface into another one. It could be much simpler if Catalyst only cared about the web related processing.