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

https://paxtonsexpertop-ed.zenbloomer.com/posts/why-do-lists-and-stories-love-the-number-7

The number 7 is seen as lucky in slots and pop culture because it often appears as a winning symbol, like the classic 777 jackpot on slot machines. It also feels familiar since we have a seven-day week