Others' problems

I would like to ask whether there is a reason why some people are curious about what other people feels and think, and willing to listen to them and try to help them just by talking and discussing the problem, while other are not. These second ones prefer to focus on themselves, seeing only their own problems, which becomes incommensurably big and feel like they have never been experienced by anyone before them - just because they don't know, because they do not care about what other people live.

I have just seen a nice movie which gave the starting hint to this discussion. Apparently, people never do anything without any clear or hidden interest. So, if they really want to listen and help others, it is probably because they might learn from others' experiences and maybe find answers to own questions. At the same time, they might feel not useless, because someone was happy about talking to them and also might have just needed those few words to take a decision or to see clearer in the problem.
Why would then other people not use the immense amount of experience that anyone could share, and maybe prefer to pay a psychologist for getting help? Maybe they can not stop thinking about only their problems, and everything would be so much better-sized if a comparison with other problems would be allowed.
I might not think right now about serious health problems, or really existential-mining situations. Although, someone said, the attitude is the first step for finding the right solution - which might also just find out how to best live with the problem.