Build a distribution which suits the needs of its developers.
We want the system to be easy to understand and extend. We don't want to prepare for all necessities and build a complex system which in 90% of all cases is overkill. There are distributions which already cover that. Simplicity also means that we want a light system, stripped from unnecessary files and features, such as national language support.
Note that simplicity doesn't scale, making something "just a bit" more complex isn't "simple" anymore.
We want to use and push new libraries, tools and kernel features where appropriate. However we're not a testbed for experimental technologies, so "latest stable" is what we aim for.
We don't want to build the Linux distribution for the masses, and we expect users to read the documentation of applications as well as for the distribution itself. The target audience also influences the design of utilities. They're meant to be "tools", not "assistants"; they should do the work for you, not the thinking.