One can wonder why in the modern world where the hardware has such a great performance, software developers would use embedded systems? There are many high-level programming languages that need just an OS kernel (preferably Linux or Android) and an interpreter to make anything possible, but at what price is that?
An embedded system can be designed to do exactly the job that is needed and in most cases it doesn’t need the complexity of a Linux like OS and most importantly doesn’t need that great hardware performance of multiple gigahertz. Well if you are developing a video encoding/decoding/streaming program a few more megahertz might just be what you need, but the most usual applications of embedded software require just a few (50-100 200 max).
One fact that you the reader might find interesting is that most automotive embedded systems (like cluster, sensors, body controller and more) work with less than 20MHz processors for the standard models, and for those of top class cars with big LCD screens systems integrate up to 200MHz MCUs.
Another aspect that makes powerful systems not applicable everywhere is that because of the high frequencies they use, not only for clocking, but also for communication and other processes, they emit quite powerful electro-magnetic pulses and thus create electro-magnetic fields. How can such solution be integrated in industrial environment? Or imagine an audio device with analog and digital audio going all around the device and a magnetic field that causes a disturbance and glitches in the audio data…
From production point of view embedded systems are much more adjustable when it comes to price. If your product is a simple one you can use as simple chips as it is enough for device to be fully operational. That’s why a common practice is to develop a product with chips that allow more flexibility (i.e. more periphery, more RAM, more FLASH, …) and when software development is over and comes time for production, squeeze hardware to the minimum to achieve the highest level economy of scale.