Many individuals who perform volunteer work in the human services field have good intentions, as lots of them want to help others and make a difference in their lives. And their's always people who want the help from volunteer workers. However, while some people will tell you, the volunteer, about their issues and do what they can to help themselves, their are others who like to tell you their issues, yet when it comes down to it, will not do anything to help themselves. To me, if someone tells you about their problems but does nothing about it on an occasional basis (but generally does what they can to help themselves), then that's fine. We probably all express our issues to others and do little about it once in a while. But when someone tells you their issues and does little about it on a regular basis, then that's a problem. It's an unfair position for them to put you in. Volunteer work in which you try to help others by hearing their issues can be rewarding since you often can help them. However, if you come across someone who expresses their issues to you but does nothing, you shouldn't have to put up with it. People don't have much patience with those who expect others to hear their issues but elect to do nothing...and with good reason.
A good friend of mine had a way of dealing with this, on a friend-to-friend basis, anyway. I (or somebody else) would start to talk about a problem, and she would say: "Are you just wanting to vent and need a sympathetic ear? Or do you want me to help you find a solution? I'm fine either way, but I like to know before we start." Bang. Brings the whole issue into focus quick.
Sometime, as jannert mentions, people really just need someone to listen. They may feel hopeless/helpless about the issue, it may be something that the emotional strain of has just drained them of energy to try - and they just want someone to hear their pain and frustration without making judgements. There are times when that's the best help one could possibly give.
As a husband and and a man, this is something I had to learn very early on. Whenever my wife came to me with something that was bothering her, my first instinct was to find a solution to the problem when all she really wanted was for me to listen to her and let her know that I support her. I had to learn how to be supportive without being 'Mr. Fixit'. On the other side of the coin, I'm not going to sympathize with my cousin who spends all his money foolishly, then complains to me when he is broke. I won't lend him money, but I would help him budget his finances more effectively if he ever asked. (Which he wouldn't.)