Not every engineer knows how to design a absolute rotary encoder, but some people know how to manufacture it. Designing complicated devices is part and parcel of modern technology. Every day, engineers from all around the world design complicated devices that help people live better lives. An average person does not even know how most devices work. The good news is that you do not have to know how things work. The important thing is to use technology and devices to your advantage. If you lack something such as a device, it is very likely that somebody has already thought of that and invented a device you might need. Inventing new devices takes time and other resources. With years passing by, newer and newer devices enter the market making the lives of people easier. One hundred years ago nobody even thought about anything like encoders. People had different things on their minds. Today, you probably also do not think about encoders very often, but at least they make your life a lot easier and more enjoyable. Next time your child asks about an example of wonders of technology, you will know what to respond. Life without technology would not be as easy as it is today.