I was at PARC in 1984, working with Dan Ingalls. I mentioned I was surprised that Smalltalk had no concurrency†, that the UI (let alone the system) was completely single-threaded. Only the window with focus could execute any code. Dan being Dan, he immediately got to work making a form of concurrency happen, followed by a delightful orgy of researches playing with the new toy. I loved it.Because: sometimes in isolation you miss important things going on in the outside world.