Have you ever considered it might be you that isn't helping others? it takes multiple people to tango.

I see lots of people helping eachother all the time. You can't expect people to just help someone they don't know out of the blue without them being able to get something in return. This is why you forge frendships- so stuff like that isn't an issue. That said, you'll find it hard to make friends if you don't do anything for them and expect them to do everything for you.