The number 7 is seen as lucky in slots and pop culture because it shows up...

https://www.generate-bookmark.win/the-number-7-is-seen-as-lucky-in-slots-and-pop-culture-partly-because-of-its

The number 7 is seen as lucky in slots and pop culture because it shows up often in old-school reels, like the classic 777 jackpot on machines. It also feels familiar and positive since we have a seven-day week