Winning a slot machine jackpot is based solely on luck. You put your money in the machine, hit the spin button and hope that Lady Luck will invite you to dance. There are no decisions to make that will change the outcome of the spin. On the other hand, many table games require skill and the decisions you make can determine whether you win or lose. Most table games when played properly have a lower house edge than the slot machines. Knowledgeable Blackjack players know that learning basic strategy will reduce the house edge to less than one percent.
Despite the importance of finding the best machines, most players don't. That's why casinos can offer both decent and lousy machines in the same casino and be confident that gamers will still play the lousy ones. They have to keep some good machines, otherwise they'd lose all the players who know what they're doing. But most of the machines will be bad, and most gamers will play them anyway. Heck, in Vegas even casinos and supermarkets have video poker, with absolutely terrible paytables, but people will still play them rather than going across the street to a casino where they can get seven times better odds. Go figure.