Welcome to bitcointalk forum. Anyway, I haven't been able to gamble for quite some time but knowing that there is a verifier that you can use to determine the fairness of the gambling site helps you to know if it is fair or not. In my opinion, this is mucu useful for those who gamble decent amount of money and those who want to provide a review of different casinos and sportsbooks.
Even if we know that the gambling site is fair, it won't affect the fact that we still lose more in those sites than win. But it's not that useless of an addition, at the least we know that the sites we're playing in are fair, right?