I have worked with many linux or unix os? Why is the user interface (UI) not so rich in its look compared to other windows or mac?
If we can back up and talk about the Linux and open source world for a minute, as opposed to the specific kernel and core operating system:
Open source communities organize and manage projects differently than for-profit companies. Different groups have different priorities and can produce really cutting-edge 3d desktop effects and incredibly lean minimalist interfaces. The cool part is that the underlying operating system, core toolset and software management systems are largely the same either way.
Anyway this isn't really a programming question and is probably off-topic. I think you're going to strike a nerve, though, because it's almost like saying open-source OSs are inferior in some way to Windows/Mac.
