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

https://paxtonscoolchat.readspirex.com/posts/what-are-the-seven-steps-in-a-hindu-wedding

The number 7 is seen as lucky in slots and pop culture because it often symbolizes good fortune. Classic slot machines like those at MrQ feature the triple 7 or "777" combo, which is a winning line