Never question psychology. I can always get away by saying you are not thinking deep enough.
(And this thread is also amazingly awesome from a psych PoV)..
In reality, it varies. I've seen all kinds of teachers, including ones who seem to be primarily motivated by the passion to teach. So yes, agreed and disagreed.
Now to the financial trader part. Traders get hooked to their job because of the betting aspect of it. Most men have that betting strain in them, and if you're paid to bet, what more do you want! At least this is the case for a big number of my classmates who are traders now. So when I apply my earlier theory here, the impediment to be cleared for traders to earn money is volatility. And they hate volatility. Or you could say it's unpredictability..
Anyway, way off-topic. Can take this to PMs if interested.