I have never heard of 7 being a lucky number in western culture and your link doesn't support that. 3 is a lucky number, 13 is an unlucky number, 7 is nothing to me.
So I don't think its that, 7 is still a very common "random number" here even though there is no special cultural significance to it.
So I don't think its that, 7 is still a very common "random number" here even though there is no special cultural significance to it.