Not if you want to do it better than the competition. We already have a zillion radio chips that all do about the same thing. If Apple (or any other company) wanted to be 'better', building a better design to do the thing in a better way (think efficiency, power, speed etc.) would give a unique advantage that cannot easily be copied by a competitor. Same goes for the RTOS (or lack thereof) that you need to run those. For some implementations, a softMAC vs. fullMAC makes sense.