It's not a scam, exactly. It's rigged so the casino / state / entity running the game makes money. That's the whole point of running a business. By Nevada law, a slot machine must pay out, *over time* 85% of what's put into it. That still means the casino gets $15 out of every hundred dollars bet.
Casinos maintain slot machines to make money. State run lotteries, not to be generous to citizens, but to make money.
Late husband once won $10,000 on a lottery ticket. My guess is over the years he spent double that, at least.