Let's not forget, German hot dogs are also much bigger and more juicy (so I have been told) than American variety.
You learn to use an in-house system and when you leave, the skills you developed remain in-house. It's like a floor trader when the pit is closed and he is forced to trade electronically and everything you know can work against you. Very few of these types of traders know how to trade without all these props so selling hot dogs makes a lot of sense. If you know how to trade then you are never out of a job anywhere in the world if you can get an Internet connection. For the cost of setting up his business he could be day trading but he is drawn to the one where his skillset is best suited.