The heat pump operates almost 24 hours a day, every day of the year. This means that it is under considerable load. Even when not actively heating or cooling spaces, it remains on, although in a dormant state during that time. Throughout its lifespan, it is exposed to wear and tear on systems and connections. If these are not regularly inspected, potential wear and tear can affect the efficiency of the device, increasing the chances of various major malfunctions.
You probably feel much better about safety, potential new issues, and fuel consumption after a car service. The same goes for heat pumps. The difference is that cars operate significantly fewer hours per year and also require an annual service check.