Because: * Some languages don't run on some platforms, e.g. C# doesn't work well on Linux. * Some languages are hard to build (for real projects), e.g. C or C

Because: * Some languages don't run on some platforms, e.g. C# doesn't work well on Linux. * Some languages are hard to build (for real projects), e.g. C or C++ projects, Python with C extensions on Windows. I don't have a good time to build Haskell projects (on Linux) either. * Some languages require a huge runtime (either install seperately or bundled), e.g. Java. They take a lot of time to download and install, and occupy a lot of disk space and memory.