the inputs for the atmega device have hysterisis, then the sensor switches can be connected directly to the device, eliminating the 74HC14 completely, reducing the component count to a minimum.
I don't know how the hysterisis (either on the atmega or hc14) would have eliminated the need for debouncing. Your circuit would have worked with a non-ST gate and the atmega, with hysterisis, would malfunction without a debouncing approach.