Yes, we are often selfish, but most people will do selfless things that give them no real gain apart from maybe feeling a little better about themselves (as you say). When it comes to life or death situations then you may see extreme cases, but you will see minor ones every day. If we were all totally selfish then the world would be much worse. It's bad enough with people trashing things for short-term gain.
I'm not looking for a debate, but I would say that you don't have to be religious to do good and being a believer does not necessarily make you a good person.
When it comes to Hive most of us are not getting rich. If we want it to gain value then we need to make it better for others so they stick around and encourage others to join. I do what is fun for me.
“ Yes, we are often selfish, but most people will do selfless things that give them no real gain apart from maybe feeling a little better about themselves (as you say)”.
That is the reward. But it is still a good act.