I think a lot of people learn a given language by hacking away at something they either want to create of modify. For example, in web development, I'd say most developers haven't ever read a cover to cover book on JavaScript.

I've tended to take the opposite approach, read first so I can at least grasp what I need to look for, then start applying. This of course is a mixed bag for rapidly changing/evolving tech and newer languages.

I take the same approach you do. When mentoring new developers I also start them off by assigning them tasks to read the docs for the core of the language we are working with.