Every time my dad plays, the ball rolls down the playfield, hits the flipper and rolls straight into the drain. Then, a second later, he hits the flipper button, turns to me and says "THIS THING CHEATS!"

A local store has two pins off in a corner, often dirty and in need of repair. I'm playing one when two teens come over. They get change from the machine nearby and the first kid plunks two quarters into the open machine.

Kid 1: "it's not doing anything!"
Kid 2: "Did you put in enough?"
Kid 1: "It says two quarters per play."
Kid 2: "Put in more."

Kid 1 inserts two more quarters and nothing happens. They start banging on the sides and shaking it but finally give up and walk away, grumbling about how ithis stupid machine ate their dollar. After my game ends, I walk over to check it out to see what's wrong.

They didn't push the start button.

While this was happening I was concentrating on my own game and mostly observing peripherally. I also assumed incorrectly that they did press the start button, because these machines aren't well looked-after and it's not outside the realm of possibility that something was broken. I did play one ball of one of their credits before handing the machine over to a little kid who was nearby.

It's a machine and machines have start buttons and that's a fact of life. You wouldn't put clothes into a washing machine and just expect it to magically start a cycle. No one stares at a blank TV screen waiting for it to read their mind and know to turn on. So no - no guilt here.