The Operating System is how we interact with the applications. It's simply a tool we use to interact with the other applications we can use.
Making it "Lighter" should be of utmost importance. Why would you want an extremely complex and heavy OS? If the OS is 100GB and takes a minimum of an i3 to run then it's using a TON of resources and you ahven't even gotten to the primary part of using a computer, the applications.
No one just sits there in Windows and never runs something. Your goal is to run an application and with the OS taking up so many resources you'd need a far faster PC. What's the point of an extremely complex OS that's running Firefox, vs Windows 8.1 (or even a Linux Distro), that could do it using far less resources and thus allow you to do multiple things?
In the end, the OS lets us interact with the applications. It's goal should be to be light and capable. Making it heavy, complex, and take extra resources is in no way the ideal.