I remember an incident where I helped someone, and it ended up hurting me. I was flying back home, but had arrived early, and they overhead paged asking if someone spoke Chinese. There are different dialects, but it was Oakland Airport, and I guess they didn't know very much.
Anyway, since I had time, and these were pre-TSA days, it wasn't very hard to go back out and get back in, so I went to see what it was about. Happens there was a guy trying to get to Las Vegas, and didn't speak any English.

So I tried to help him get a ticket by asking at the counters. Ended up going with American, cause it was cheapest. He only had cash. They had no change. The lady was very rude and wanted to verify he had no change, and reached forward to grab his wallet, but I refused to let her do that. I ended up paying with some of my own money to get him to the proper amount.
And off he went, and off I went on my own way. Then Southwest gave me trouble for me missing my flight, but I told them to rebook me and they did (I had a refundable ticket anyway).


But I think (in the same vein as others have written) you help others not cause you want anything. It does make you feel good.
Recently there was an article about a lady who was helped by someone seated in the first-class cabin when she was struggling with her baby and all the associated equipment. She was thankful he gave up his comfort, his ability to get off first.
I think many times people, especially those on flyertalk (because many fly in the premium cabins), and myself, forget how to act like a genuine human being because we're so into getting out "premium" stuff.
This past week I helped someone getting the suitcase down (sometimes you have to go down steps outside, to board these small propeller planes. At least in Seattle you do). That felt good. And then when getting off my most recent flight there was a guy in business, who hadn't gotten out with the first bunch, and so was waiting for a gap in the passengers coming from economy. I let him in, and he flashed a grateful smile. Why shouldn't he get normal courtesy, just because he sat in business? Why is everybody in such a rush?