Wrong for 2 reasons.

1- In my belief, people are postmen. What they do is carry messages. You kindly thank that person. But you don't feel indebted to them.

2- If Smo does not believe in God, it is still wrong.

The definition of "good" is something done without expecting anything in return.

and the feeling of "gratitude" imposes a sense of indebtedness on people.

People who think that they is doing good thing say,

"Look, I did this to him/her. But he/she acted like that. He/she was not grateful at all."

So it's waiting for a response.

This is like trading.

It's not about doing someone a favor.