System stability and efficiency(optimal power factor) are the main challenges for system engineer. Within stability limit the power factor closed to unity would give higher efficiency and could be achieved without loosing stability of system by modern battery backup with used solar power generating stations in load areas, along with solar domestic power users, though it depends on intelligence of engineers……
Power factor must be unity means capacitive reactive power in loads and generation equal inductive ones. The system comes to pure ohmic circuit. Cancelling the reactive power in the system would reduce voltage drop in the transmission line hence we get constant rated voltage at the load.