Earning rewards points on credit cards is getting harder after two of the big banks cut the rate at which points accrue.According to comparison site Mozo, over the past couple of months ANZ and Commonwealth Bank have reduced the rate at which points are earned on their rewards cards. For ANZ customers using a standard card, American Express cardholders now earn 1.5 points per dollar of spending, down from two points, and Visa cardholders earn 0.75 points per dollar spent, down from 1.5 points.For ANZ platinum cardholders, the reduction is from three points to two points per dollar on Amex, from 1.5 points to one point on Visa and from two points to 1.25 points on Black.In February, Commonwealth Bank reduced the Qantas Frequent Flyer earn rate on its Diamond and Black cards, cutting the number of QFF points per Commbank Awards point by 20 per cent.And Bank of Queensland ended the bonus points offer on its Blue Visa and Platinum Visa cards.