For development, having full access to the AST at will is a definite good reason. Having such allows you to analyze your code as you're writing it in much more

For development, having full access to the AST at will is a definite good reason. Having such allows you to analyze your code as you're writing it in much more intimate ways, allowing for better refactoring tools, better error analysis, better variable completion, etc. Additionally, because of the modular format of clang, pretty much every build is a cross compiler. You don't need to rebuild clang to get support for arm and x86, for example. There's even targets for GPUs, so you can use the same toolset top to bottom much more effectively.