You are correct that they were designed around luck. That is precisely what they were created for. That being said, all of what you think is cheating is perfectly okay in pinball. Now, the extent of how much of that is done as others have said can be adjusted to be tighter or looser. I personally do not think people need to beat the hell out of the machine, but even I have almost put a shoulder out trying to nudge a heavy machine.
Rubbin's Racin'