This could sort of apply to arcade machines in general, but it's certainly true of Donkey Kong.
Has anyone ever felt that it was extremely inefficient, in a system-design sense, to dedicate not one but two buttons (or any buttons at all), complete with all the physics and wiring thereto, solely for the purpose of starting the game?
You could put your quarter in and just as easily hit "Jump", or wiggle the joystick, to start the game. Doing it that way you'd both streamline the design and save a significant amount in manufacturing and maintenance costs. Consider all of the electrical and mechanical parts (and the resulting potential complications) that you're introducing to the system with those impractical and superfluous buttons.
I guess the psychology of it was considered (or determined to be) profitable enough to justify the extra investment. After all, everything about the design of these things is exploiting psychology in one way or another. There's definitely a feeling of power/agency in pressing a specific button that does nothing but start the game. It also had to be idiot-proof and extremely straightforward/user-friendly to someone unfamiliar with such a machine.
I guess I answered my own question...
Another question, almost a more important one, what's the point of a two-player game of the "alternating" style, given that the players' individual games are 100% compartmentalized and in no way affect one another? Why not just play two one-player games back to back? Having to alternate is just obnoxious! Actually, a two-player game between any two members of this group is kind of a funny proposition: you'd play for a half hour or so, then get a totally unpredictable break of anywhere between 30 seconds to an hour!
Have any of you tried that with one another at some point, just to annoy yourselves?
The two player thing is, no doubt, psychological too, and must have become "industry standard" for a reason. That one I can't answer myself and I'd be interested in knowing the reason.