There's a slight difference in abstraction level there. I've done more than my fair share of stepping through assembly in my life and learning things from even minified JS is a lot easier.
But I don't think many people learned programming by studying random real-world programs in a disassembler. It was once at least theoretically possible to do that with web programming, albeit not well and not anymore.
Why not? You can step through an assembly program just as easily as a javascript one...