Even the soothsayers may not accurately predict games all the times. If not their visitors would consists mostly of gamblers who are in search of solutions. Generally, the gaming niche is not supposed to reach this length of inviting a prophet to forecast competitions. Wouldn't it cost the player extra money to consult the powers of spiritual eyes?
Now, for example, there are players who really want to win but need guidance from a fortune teller, it will cost more and it seems that players have to spend more money just for guidance, not with the amount of their victory because with the amount of their victory I think it is not certain.
Let's assume the player won, whoever was responsible for the prediction would want a share, and the gambler will also go back to them for their next prediction. The whole revolving processes diminishes the fun of gambling as the complete earnings no longer goes to the winner. He'll now go back and forth to please the soothsayer's demands from him. It's not worth considering.