Hello Gents,
Linux' approach to computing is modular and open. In Linux, libraries are dynamically linked eliminating the need for developers to write new libraries for each application.
In Windows, it is against the law for a developer to make use of another developer's library without their consent or most likely a fee. In Windows, more often than not each tool comes with it's own set of libraries and tools that can only be used by the user and the operating system, but not other tools. As result, the whole operating system is just a bunch of duplicate, incompatible and ridiculuous amount of libraries and tools. It is plain horrible.
On the bright side, Linux follows a completely different approach to computing. There is a set of dynamically linked libraries which can and is shared by all tools and applications. As a result, devs can write code to make use of these libraries, without any legal constraints or fear, and even add to the libraries so that other devs can make use of the libraries too. The result is that there aren't any duplicate dlls, all of them are compatitible and things organised.
Modularity: Rather than right every tool on earth for a single application, in linux it wiser to make use of tools already written, again streamlining the size, purpose and objective of developers, with regards to writing tools and apps. In Windows, every developer has to right it's own tools for it's own application. Developers can't share tools with other "non-operating system" tools.
The instances above are just a few reasons why Windows needs an oil change on regular basis than Linux does. I hardly use the "emerge clean" command line. Which reminds I should do one now and see if there is anything that need be cleaned. Linux is a lean mean machine in that bloat is usually cut down by 75% per application as compared to Windows.
It's funny how very few people don't realise these as the glaring difference b/w Windows and Linux, I've used the above to woo quite a few people to start to consider using Linux. That's also why performance wise, Linux will always be faster and more stable. Security is another story all together.
I imagine there are maintanace tools/utilities to make you linux box even more leaner. I'd look into that and return if my search is successful, or someone might beat me to it.
NOTE: Warning, never ever delete you /lib directories. Don't ask me why.