fungus:
delay() is the Devil's Function. Tempting newbies in, making them think they're doing real programming when all the time they're only digging fiery pit for themselves
and thumbs up/like!
Otherwise I'll chime in - Using the millis() and two lines og code does do software debouncing without any real overhead better/as good as any hardware solution. It may be your buttons do not hold the contact but have such a lousy contact (high resistance) that you dont see "bounce" but more of a "cant quite keep the circuit closed". To test do loop() with only Serial.write((digitalRead(button)==LOW)?'0':'1') and look at it. An oscilloscope would be better.