Why? There has to be a reason for this. You don't just accidentally help people out.
Because I believe in helping other people. People gotta look out for each other. And, for the record, it's very easy to accidentally help other people. I believe altruism is good for the sake of altruism.
You have posted this on an online forum. By making this public you reveal that you have sought to increase your own positive reputation.
An almost-anonymous forum filled with people I hate. Even if that had any positive contribution on my reputation, that was not my motivation.
Subconsciously you were hoping for good feelings and/or trying to avoid any bad feelings from not doing this.
Nope. If I wanted good feelings, I'd go buy a bag of drugs. It's a lot easier to consume chemicals to feel good feelings than to pick up a piece of plastic for twenty seconds.