Come from Nevada I see - Seven is only a "lucky" number when it appears on the "Coming-Out" roll at Craps at that well-know Nevada hotspot - not that I've got a lot of experience at the game! As seven is the most probable combination using two dice, this is the best chance you get to win until the point number is established.
Once the point number is determined, seven is "Craps" - you lose!
Off to historic York in the coming weeks - Old York, the real one where the railway museum is...