The number 7 is seen as lucky in slots and pop culture partly because of its...

https://zanesnewthoughtss.evergrovio.com/posts/why-does-seven-show-up-in-calendars-religion-and-games-at-the-same-time

The number 7 is seen as lucky in slots and pop culture partly because of its long-standing role in the seven-day week, symbolizing order and completeness