IoT allows devices to be controlled in ways that were not previously possible. In the past, physical proximity was a requirement when interacting with devices. Engineers connected mechanical or electrical devices to perform or respond to a localized physical event. The proximal mechanical connection limited the ways to control the device. Today, microprocessors with advanced communications capabilities are inexpensive and easy to design into products.
Physical and proximal access that constrained past interactions are now performed with a command sent wirelessly or via wire. This freedom allows things to be controlled in ways not previously imagined. It also allows for the creation of IoT ecosystems. For example, cars, homes, and factories now contain rich collections of IoT devices. They sense and control one another using data rather than rigid mechanical systems.
Data communications provide tremendous flexibility in device use. They eliminate the need for a physical presence or physical connections.
What really makes IoT so important is that we as a society now rely on these connected devices to perform critical functions. Self-driving cars are a good example of something that is safety-critical to many. This includes the occupants of the car itself, nearby cars, pedestrians, and structures. The potential benefit is yet to be fully understood. That also goes for the potential risk of something going wrong.