Encouragement vs apathy

At work I try to be as encouraging as possible, particularly when it comes to people who are less experienced than I am.
Lately it has become apparent, I guess moreso than normal, that there is a large amount of apathy among some of the people I work with. And it frustrates the heck out of me.
For some people it seems as though it is easy to have a low care factor about what they are doing.
I physically can't do this. Unless I'm under the weather a bit I am really enagaged with what I'm doing, always thinking about things I can write about and keeping up with what's going on. Basically if anyone rings our office with a technical question it ends up with me to explain or help with the problem.
I have wondered a bit recently what would happen if I wasn't there.
Clearly my expectation of the people I work with, one or two in particular, is higher than everyone else's. What I can't understand is why they don't just love what they do - we don't have a high risk job, we're not responsible for saving lives and we essentially call our hobby our job. At least that's what it's like for me.
From the outside it appears that for some it's just a job and mediocracy is acceptable. Now I am not a high-flyer and never will be, I don't aspire to massive heights within my job (except for one particular step) but I love what I do. It just seems to me that I'm in the minority there and that's sad.
Sometimes it feels like you're swimming upstream, fighting against the current when everyone should be heading in the same direction.
It's hard to be encouraging in this scenario but I try, though I've got to admit I'm close to my last attempt with one of my coworkers, even though it's not my job to push him at all, who has all the talent in the world but is just not using it.
I know it's not really my business, other people's work ethics, but I just want what's best for the team and when I'm giving 110% and look around and see others giving 50% it's disheartening.