Because of the time an knowledge it takes to blink a LED. When you are complete newb, you can't diagnose and fix problems. By definition you can't yet understa

Because of the time an knowledge it takes to blink a LED. When you are complete newb, you can't diagnose and fix problems. By definition you can't yet understand how things work which is prerequisite to debugging. This first step is then most critical -- if it doesn't work immediately many people will be just put off completely. If it works, people can tinker with it, see result, learn, etc. They can't learn in the absence of feedback. Newbs will not be able to judge if IDE is "poor" or C++ preprocessor is "horrible". What's most important is that it works right away.