Simply put, they grow to hate it. After a while, a trader will sit at his computer and say, this stuff is so beyond stupid. They will never be able to tolerate dealing with a probabilistic work environment every single day enough to get over the big hump and into profitability. And to take it a step further and probably more important, they cant work in a world of subjectivity. You can have 10 different traders giving you 10 different reasons why a trade may or may not be ok. And maybe all 10 of those traders are profitable but the lack of clarity and subjectivity are enough to drive a learning trader nuts. Imagine working at a pizza shop and everybody in the room is giving different instructions on how you need to cook the pizza in order for it to come out good. You would take off your apron, throw it on the floor and storm out yelling, 'you people are a bunch of wackjobs!" Well, this is the trading world. And quite frankly, it sucks.