I attended public school all my life, middle school through graduation from HS went from '78-'85. I was never told to wear a jock strap or a cup. I also played little league for four years during my youth; same deal. I've run a bunch of marathons, 1/2 marathons, and endurance/mud runs... never wore a jock or a cup.
At one point as an adult, I was participating in some sport, can't remember what, and decided I should probably protect the boys. I couldn't figure the fucking thing out. Wearing the jock without the cup just sort of squashed the whole package flat, and things were squeezing out to the sides. That can't be it, it sort of defeats the purpose of the thing. So I slid the cup in, and it didn't get much better. The back of the cup sleeve- the part up against my genitals- was stretched straight from one side to the other, resulting in things getting squashed flat again.
I wrestled with it for 15 minutes in my bedroom before taking it off and throwing it into the back of my drawer, never to be worn again. These days, a pair of running shorts with the wicking inner layer keeps the boys comfortably nestled.