The question is when you take a setup do you know why you are taking it and what this means in terms of the underlying activity that should support it going forward.
The mechanical trader probably does not care much about this. He's backtested and happy with expectancy so leaving his stop is just part of plan. Hence, some of the quotes above. This is not a criticism, simply an observation.
The discretionary trader is the opposite. He's aware of the why in terms of the what. Therefore, if the what (price action) does not occur he's out regardless. This is also why he does not need to place a hard stop on entry. If you think about this, this 'expectancy' has nothing to do with prediction, it is in fact the ultimate trade what you see approach.
The trade either behaves right, or it does not and in a sense this is his first stop. A hard stop or even a mental technical stop are really only backups to what he sees as correct price behaviour.
I don't think I can add anything further by way of explaining this viewpoint.