Another suitable task for a microcontroller would be a basic user interface. Hectronic used an 8-bit microcontroller in an application of a customer to control a user interface with a couple LEDs and buttons.
Not much work for any microcontroller, but still a relevant example. In this case the microcontroller may also be used as a stand-alone user interface communicating via CAN. It would only slightly increase the complexity of the system while extending the level of flexibility significantly.
Microcontrollers can be used to realize serial interfaces like I2C, SPI, CAN and UARTS. Monitoring of temperatures and fan control are other examples. In addition microcontrollers are excellent at implementing GPIO interfaces of almost arbitrary sizes. There are a lot of possibilities.
In an environment where a minimum or maximum temperature is required to start a system, a microcontroller can be used to run pre-heating or cooling before the system is started. In this way a cheap industrial temperature microcontroller can make sure the entire system does not need to meet the same temperature requirements.