Everyone serious enough about his work to care about efficiency. And no one prevents a self-taught programmer to learn algorithms techniques (or anything at all, really) but the chance of one doing so are really low, especially considering that people opting for a 12-week course instead of a 4+ years-long route aren't the kind you would think of as particularly dedicated to something.
That's a great question. Maybe the fact that they don't even think to look for such a thing?
I spent at least 10 years doing development on my own before university and it never once occurred to me to read an algorithms book. Funny enough, that turned out to be one of the best courses I ever took.
I think with the rise of MOOCs though and the offering of algorithms courses for free online, such as at Coursera, there are going to be a lot more developers without formal education who are familiar with algorithms.