Slots are a random luck game. You don't wanna sit there and keep spinning a slot thinking that a bonus has to hit. Spin 50 spins and if no bonus move on to another slot and keep repeating. A slot is not programmed to hit a bonus after x spins, they just hit when they hit. On average you will hit a bonus every xxx spins, but noone knows what that number is exactly. You spin a slot 1000 times, by the time you hit the bonus you'll likely be down 500x on the spinning and a bonus wouldn't get you even in most cases. So, avoid that strat.
This type of slot gambling is indeed very related to luck, even it is closely related because it is true what you said, this type of game is not programmed, but previously the dealer must have arranged everything to make him succeed in getting more profit than his players, therefore many people who experience defeat become something that is normal, I once got x500 and that was only once during my gambling.
another ridiculous thing is that there are people who believe that the strategy they have can make it easy to win, in my opinion it will not work as smoothly as what is thought, the strategy they have is like encouragement for themselves to be more confident in gambling.