The number 7 is lucky in slots and pop culture because it's long been a symbol...

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

The number 7 is lucky in slots and pop culture because it's long been a symbol of good fortune, partly thanks to the classic 777 jackpot combo on reels