Luck here isn't referring to some invisible dice roll whose randomness can not be explained or is just a correlation (like no rain on your wedding day would be)

Luck here isn't referring to some invisible dice roll whose randomness can not be explained or is just a correlation (like no rain on your wedding day would be), it's refers to variables that the person can not influence. Being born into a rich family is lucky for that baby, and the baby can't have done anything about it.