Why use Sass? I get by with CSS just fine. I don't need another layer of complexity.

CSS is not fine, it's full of hidden tricks and workarounds that are unintuitive and a burden to remember and implement.

Is remembering the correct vendor prefixes to use for border radius or gradients are good use of brain time? Do you like managing image sprites? Focus your energy on hard problems that should be hard, instead of remembering how to float things without exploding Internet Explorer.

Let's talk about how to build your own Sass and Compass tool belt to save you time and energy to focus on the important problems.