Certain customers can be trusted. Some customers have the intention to buy more items but they soon realise that they don't enough money to pay. If they are regulars, I don't mind letting them on credit. They would surely come back to pay me.
But certain customers take it for granted. When I give them on credit, they don't come back again. So in this case, I lose some money.
So at times, I rather don't give any credit at all..