Actually your analogy goes more the other way. My minivan is nothing like my suburban from when I was a kid except for having a steering wheel and a gas pedal. Pushbutton electric start, automatic transmission, power steering, automatic door locks, wireless key fob, bluetooth stereo comes on by itself without asking me, and probably next year it will be an electric vehicle with completely different mechanical characteristics. Basically, /bin/bash is the same and you might compare that to the steering wheel.