Why do some members stiff me?

I don't think it's just here on the forums. I've noticed that in life, some people just act like you owe them something.

At work, I provide a service. I make that service appear easy and perform it quickly. Some people think just cause I did it quickly, they don't need to pay me. If only they'd offer, I'd just say no charge. But at least offer.

Some people have become very self centered and uncaring about their neighbor.