Because you don't always need a mansion-sized Sass grid library.
With no offense intended towards the incredible, robust and flexible Susy (I personally love it), I bring you Condo, a tiny Sass grid library.
The philosophy of Susy seems to be to provide the developer with a broad palette of tools and almost limitless flexibility in creating a grid system. Condo's philosophy is to create a limited tool set designed to accomplish a discrete set of grid layouts.
Condo utilizes similar variables, functions and mixins to create grid systems as Susy. You will recognize
gutters() from Susy, but not all the features you're used to will be there. In the right context, this is a very good thing.
For example, Condo does not support right to left layouts, only left to right ones. My apologies to any developer out there who needs right to left support, but I never have. Rather than working this into Condo, wasting compilation time on checking a setting that I would never use, I recommend forking Condo, flipping the output and naming it "Odnoc". Give me some credit if you're feeling charitable.
You'll find other, similar restrictions throughout the documentation.
Condo is available as a Bower package and a Ruby gem.
$ bower install condo
Ruby Gem: Sorry, I couldn't get the same name for the gem