Many times when you hear from those, such as firefighters, who risked their lives to save one or more people, afterwards the heroes will say that they were "Just doing their jobs." But to me, even if risking their lives to save others is a part of the job description, it doesn't make them any less of a hero. To me, they're just minimizing what they've done. I have a lot of respect for those who risk it all to save others from death, regardless if it's a part of their job or not.
I think it's one part 'don't want to sound smug to the people I just saved' and other part it literally is their job. They're paid to put their lives at risk to protect others. I agree, though, they're still heroes no matter what.
It is their job, but I think what you might not understand is their mindset. Perhaps for them, it's normal to risk their lives for perfect strangers. It's the rest of us that might be abnormally selfish.
I feel like some people don't mean that, but they say it anyway. I feel like others really do mean it and I have all the respect in the world for that.