As others have said, many very simple radios do demodulation in mostly analog circuits, saving the digital stuff for only the last step (or not at all, for tota

As others have said, many very simple radios do demodulation in mostly analog circuits, saving the digital stuff for only the last step (or not at all, for totally analog systems like an FM radio). The other thing is flexibility. If you don't need to change your demodulator, you can do all your digital signal processing on a purpose-built ASIC, which brings the cost way down. Radio demodulation and decoding typically falls in the "embarassingly parallel" category, so it's an excellent candidate for efficient implementation on an ASIC or FPGA.