Any coin-op was obviously trying to walk a tight rope between maintaining user engagement and making it hard enough that you would have to spend significant sums for training purposes. Otherwise you might as well give players 999 lives.

Proof: there is no technological limitation for modern coin-ops regarding saving state, but games actually implementing some sort of saving mechanism are still few and far between (and even then, saving features are almost invariably another way to force players to buy add-on gizmos...).