Soft brake pedal

Sometimes in stop & go traffic after repeated stops, brake pedal almost goes to floor. Brake pads were worn down & rotors needed turned, but replaced w/ new ones. Did not make any difference. This past weekend took for test drive after repeated stops was ok until came into driveway w/ very low pedal. Had local Toyota dealer look at car, their opinion was everything was in good condition & working fine & charged me for it