Alright legit answer time.
Because you believe in the freeware movement. Linux is free and open source meaning you can look at it's source code. You can improve ANY Linux distro you see fit, and help EVERYBODY that use ANY form of Linux. Linux is alive because of the goodwill of the people who takes their time to code free programs for Linux. There is no benefit to coding on Linux (other than the fact it is smaller than windows, and in some cases faster), there is less options for compilers and IDE's on Linux. There is no positive, but there is no negative. Just different API's, and no selling your work.