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

https://wiki-site.win/index.php/Why_Is_the_Number_7_Lucky_in_Slot_Machines%3F

The number 7 is seen as lucky in slots and pop culture because it often appears in winning combinations like 777 on classic reels. Its charm also ties to the seven-day week, which feels complete and balanced