because slot gambling has been set in such a way by the gambling platform and very rarely anyone can get the jackpot from slot gambling, except luck as you say.
and in fact a lot of gamblers still play slot gambling just for entertainment in their spare time without expecting to hit the jackpot or luck. but there are also a lot of gamblers who believe that playing slot gambling will get a big jackpot and always expect it to happen without realizing that he loses more money is not worth the profits he gets when playing slot.
so what you say is true that slot are the worst opportunity for gamblers who expect big wins but get entertainment benefits for gamblers who just want to play to fill their spare time