I think it's more that the 555 is basically the heart of hysteretic controller in a box, but it doesn't have the other stuff you need. https://en.wikipedia.org

I think it's more that the 555 is basically the heart of hysteretic controller in a box, but it doesn't have the other stuff you need. https://en.wikipedia.org/wiki/Bang–bang_control https://en.wikipedia.org/wiki/Bang–bang_control There's still plenty of analog control out there, it's just all hidden away as parts can integrate the sensor, controller and actuator, all in one magic IC. And it can definitely be lower power and cheaper, in volume. The main weakness is the NRE is higher than the typical MCU project so it's not really seen in low volume or hobby level stuff.