I totally agree with this.
These kinds of contests (wagering leaderboard, high multiplier...) are the most effective promotional strategies for attracting gamblers and turning them into loyal customers.
What makes them even more attractive is when they are offered exclusively to a certain community. This makes the community members feel special and know that the casino values and cares about them. They create some kind of social relationship between the casino and the members of that community.
But sometimes it also "depends" because if it gives the players a sort of edge, the casino would be losing money. Plus they would be losing money exponentially if one user has
ten multi-accounts.

It already happened in BlackJack.Fun when they had their community-friendly daily/weekly/monthly wagering contests. Users were happy to win back
some of their losses after the prizes were given, plus they were given a generous amount if free spins in Dig Dig Digger. The admins were OK with losing a little amount of money because the casino was growing.
But when a
largenew group of people arrived, they definitely had multi-accounts, and exploited BlackJack.Fun's generosity because the casino lost millions from their wagering contests.
Someone said that he/she believes that the group was a team of professional exploiters from Asia.