1.14 nightmare is such an important turning point for sam. before this episode, he's unmotivated to save people, or at least he's not motivated where it conflicts with his personal goals of revenge. he's outright resisted working some cases (wendigo, scarecrow) and is willing to abandon people he knows will die because they're getting in the way of his search for john. when he is motivated to help people, it's because it relates to his own goals (home, for example) or because it personally affects him.
but in nightmare, max is a foil to sam. their upbringings were similar, their origins are the same, and they share psychic powers. the difference, according to dean, is that max is a killer, a monster, someone who is unempathetic because he's hurting people with his powers. sam sees himself in max, and importantly, he sees what he can turn into. he lets go of a lot of his anger, begins working to forgive john, and finds comfort in the fact that dean is looking out for him.
and the very next episode opens on sam pushing for a case dean is reluctant to pursue. the times sam has found and pushed a case up to this point are:
1.06 skin: he wants to help his friend (personal involvement with the victims)
1.08 bugs: sam finds the case, but the dialogue seems to suggest that dean was having sam research potential cases while dean was bringing home the bacon. uncertain origin here
1.09 home: he has a vision of jenny (personal involvement related to his vision and finding john)
1.12 faith: sam is looking for a way to save dean
1.14 nightmare: again, he has a vision of max's victims dying (personal involvement)
so based on this, it's rather rare for sam to seek out hunts unless he's involved in it some way, either through his visions or some other personal motivator. he wants to save the people he cares about, but he's resistant to saving people he doesn't know.
that makes sam pushing for the case in the benders important, because it's the first real time sam seems to be motivated to hunt for just for the sake of hunting. since it comes right after nightmare, it seems to imply that sam has decided to try helping people in order to prevent himself from becoming like max. if the circumstances were different, he could have turned out just like max: sam said so himself. and now he's extremely aware of that fact, and he's committing himself to avoiding that at all costs. the thing inside him, the visions, the rapid development of psychic powers, scares him—but dean is looking out for him. so he tries to reject the terrifying unknown of his powers by embracing dean, following his example. because dean is good, so by emulating dean sam can be good too.
