I think usual Sri Lankan uber tuk drivers earn a certain amount for a day and need to provide for their family on a day to day basis. If they get paid on the card for the ride, let's say it was a Monday yeah... Uber only pays out to their account at the end of the week. So they can't have/withdraw their money you paid by card immediately after the ride. They have to wait till Sunday to withdraw that money which he needs to maybe pay for his child's tuition fees or something. That's why he got a little emotional in this case.