> I stopped even though I agree it is the right thing to do because I felt like a fool every time I did it... why should I be the sucker who does it?

You really are a fool. Who willingly gives up the chance to get some free exercise and feel morally superior? I'm over here happily returning others' shopping carts, not just my own, and basking in the knowledge of how I'm a better human being than you maest.