The sneaky thing about gambling at casinos and other professional outfits is that the career total of any given gambler is a random walk that can easily end up quite positive with significant probability (e.g. say around 50-50), so if you poll your friends you may well find people who are ahead, which is really great marketing. The house advantage is that of course these "around 50-50" odds are in the house's favor, and thanks to large numbers of visitors they can remove the variance and profit reliably.