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

https://blogfreely.net/teresa-long85/how-did-the-seven-day-week-get-connected-to-astronomy

The number 7 is seen as lucky in slots and pop culture because it often symbolizes good fortune, like hitting the classic 777 jackpot on slot machines. It’s also connected to the seven-day week, a familiar cycle that’s part of everyday life