You mean, why would you want to have support for features like application wide refactoring, Intellisense, and build-time error feedback? Or were you asking why you'd want to be able to leverage class-based object oriented design patterns, with inheritance, interfaces, and generics?
Look in the release directory, and grab the latest prebuilt installer binary. While that's running, navigate over to the docs directory and take a look at the user guide. You can also clone and build the full Blade source code to achieve a similar result without executing the installer. If you prefer that route, refer to the user guide for more detailed instructions.
Blade is quite young at this point. We've worked hard to put together a fairly large internal test suite to try and ensure all the scenarios your try will work properly. But don't be surprised if you run into some issues. The good news is, if you submit a bug report we'll try hard to fix it. And of course, you're also welcome and encouraged to fork the project and make improvements yourself too!