Data sources?
Bonds, stocks, exotics -- that stuff is all teachable. Give someone two years and they can learn to work the markets. Currency has basically zero theory surrounding it. The guys who are really good have no idea why they're good at it. It's basically all just trapped in their heads and they can't get it out. That's why the guys who are good at it tend to stick around forever and they end up being much older than the other guys on average.
Also, with other i-banking specialties you need a larger supply train, including data gathering, analysis, packaging (as a fund) and marketing. With technical trading all you need is your computer and you. Why would a young person who is skilled at technical trading work inside an investment bank? How can you be sure that there aren't thousands of skilled traders making a killing from home? Isn't this sort of like hackers?
Why would someone who knew how to trade bother selling an $899 course? They'd be making 10-10000 times that, trading.