Why use the 8051 architecture? The core of the 8051 arguably is used more than any other device. It is an expansion of the i8042 architecture, which is the fundamental processor used in keyboards for personal computers. The architecture has been around for over 25 years. It is constantly being enhanced by various vendors to perform tremendous tasks.
Why has the 8051 continued all these years especially now that new powerful 32 bit ARM Cortex™-M3 devices are available for a mere $1? It makes sense that the 8051 would be replaced by these types of devices. 8051 devices would then be found in only a few legacy products. But, 8051s are everywhere ! The 8051 of today is not the same one from the past. It is faster, smaller, has more ROM and RAM (with banking), more data pointers (up to 8) and far fewer cycles per instruction (from 12 to 1 or 2) plus many new peripherals. It can be a chip or gates programmed into a FPGA. The 8051 continues to evolve.