Why do we do so?

Scene:1

Mohan along with his colleague was returning back from office. Suddenly the cellphone of his colleague's rang and on the other side was his son who requested him to bring a set of color pencils. His colleague requested Mohan to get a set of color pencils from the nearby shop. Mohan bought the pencils and gave back to his colleague. His colleague took out wallet and was about to give him money to which Mohan politely refused saying its just 30 rupees, no issues.

Scene:2

Next day, Mohan had to go to a nearby water park for outing, since his bike had some trouble, so he thought to hire a rickshaw. One rickshaw fellow was going to the same side, Mohan stopped him and asked "Bhaiyya kitna paisa logo water park chalne ka". "40 rupayee de dena sahab" replied the rikshawala. "Aree 40 rupee bahut jyada bol rahe ho, wahan toh bas 20 rupaye me jaate hain" answered back Mohan. The conversation contiued for a while and finally they settled for a fare of 30 rupees.

Comment:

In the first scene Mohan let go Rs.30 very politely even when he knew that his colleague can afford to give the money but possibly because of etiquette he denied taking the money and in the scene 2 we find that. He argued with the rickshaw for a sum of Rs. 10, which possibly for richshaw fello would have been atleast 10% of the day's earning.

Whether we notice it or not we all replace Mohan in  the two scenes but never wonder why we do so when we take a richshaw we argue for 10-15 rupees, when we buy vegetables we try to get the price reduced by 4-5 rupees whereas with our colleagues and friends on the name of socialism we spend 500-1000 odd rupees without giving a second thought. 

WHY can't we be more generous with these people for whoom the small amount of money matters more ?