Bus drivers were stealing bus fares by recycling tickets. Moreover, KL could only implement a single concessionary pass system for all the LRT, MRT, Monorail, BRT and bus lines if a single cashless system is employed. RM10 (for foreigners, RM6 for locals) for an unlimited day pass for all the metro lines including buses is a very good deal. You just need to buy a reloadable card (called Touch N Go) at any metro station or at the Touch N Go service center in KL Sentral. You can also use the Touch N Go card to pay for parking and tolls.