The number 7 is lucky in slots and pop culture because it's long been a symbol...

https://wiki-book.win/index.php/Why_Do_People_Still_Like_Retro_Slots_with_Sevens_in_2026%3F

The number 7 is lucky in slots and pop culture because it's long been a symbol of good fortune, partly thanks to the classic 777 jackpot combo on reels