Three Categories of Students

I've been working as a TA for six years and four months now, and I've seen the graduation of six classes since 2001, some of them are now colleagues and best friends. But what I want to share today are two things; an observation that raises a question, and another question. The observation is that I could roughly divide the students in each class into three main groups: students who are self-reliant and have a good instinct that enables them to study on their own, students who are very smart but wasting it, and students who don't give a damn about studying at all. The first category of students are mostly very smart or very independent or both, they do not want to count on anybody to study, understand, and get the grades they want. They do not come to you asking for silly questions, they wait until they encounter very difficult problems and then maybe they'll ask you for advice. I like those ones and think they have the highest potential to make something important out of themselves. The second category is the students who are mostly smart but think that it's not "cool" to be interested in studying and doing what it takes to get the grades, or they're just uninterested. I developed this belief that this is the category that needs most of the work from professors and TAs because it is a real challenge to get students in this category to be interest and if the challenge is conquered in the right way, they'll constitute a great gain in the value of the whole teaching process. The third category is the "don't care" condition. I really "don't care" about doing too much effort with this category, but I want to emphasize that by this group I mean students who do not want to learn and do not believe that learning holds any value to them. Maybe in their future when they're confronted with life choices and work requirements they'll realize their faulty beliefs, but at the current time, they do not believe in the whole process of education. Well, this specific category has caused me to think repeatedly and ask myself this question: is there something that can be done to shift their attitude, or are they a hopeless case? I couldn't find an answer to this question after six long years in service. All I could hope for is that I might have contributed to the shift of some of the second category. At one time I really thought that the second category is the one professors and TAs should focus all their efforts on, but this wouldn't be fair to the first category who need to know that they have a support system they can rely on when need calls.
As for the question, it's whether or not I should explain all the details of a subject in class. I believe that a margin of questioning and unanswered problems in class should be allowed in order to let the students test themselves and think of the possible ways of solving problems and finding outcomes. But it seems as if by doing so, I caused myself a headache of continuous "nagging" and bafflement among them. It seems that students of today -with fewer and fewer exceptions as the years pass by- do not want to make an effort on their own, they either do not want to exert that extra effort to think on their own part of the time, or they're afraid to do that because they are not sure of the validity of the method their minds work! So I found myself keeping this margin "marginal" as much as possible, and I don't think this contributes positively to them, but I'm tired of the headache they cause me.
I do not know the correct answer to those questions, nor to every single question in the various subjects that I taught, but I believe that when you're willing to break the mental blocks inside your mind, you can try and answer any question, and the chances are high that you'll get it right, is this how humans discovered fire?