The way I've heard it is: Being a microwave engineer is the easiest job in world. You basically only do two things, design oscillators and design amplifiers. What's the worst thing that can happen to an amplifier? It oscillates! And what's the worst thing that can happen to an oscillator? It won't start, but it's usually still a pretty good amplifier. Win-win!
The way I heard it was "amplifiers oscillate and oscillators don't".