Both Java and .net have debugging tools on par with what you see Casey doing in his streams. The way he debugs code is exactly the same way you would debug Java and .net code. You can set over lines of code, step in and out of functions, change memory values, etc.
You're right, of course, but proper debugging simply wasn't covered in any of the books I read or classes I took when I was learning Java, and I was relating my personal experience. In class, we spent more time on the "theory" (i.e., drawing flowcharts and UML) than actually coding, and then when we actually got to "real" coding it was a game of copy-pasting instructor-provided methods into place properly.
During my formal programming education, the CPU was a magical black box and we were wizards stringing together obtuse incantations, praying the results we got were the ones we wanted.
Compare that to Handmade Hero, where the debugger is an indispensable tool from the very start and no line of code is inscrutable or left unexplained.