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

https://chancessmartperspective.nexorafield.com/posts/what-is-a-megaways-slot-and-why-was-it-mentioned-with-mrq

The number 7 is seen as lucky in slots and pop culture because it often represents good fortune and completeness. Classic slot machines use the 777 combo to signal a big win