This is what is noticed , you placed a bet on some sportsbook on example Player A vs Player B in a 3rd game in 1st set. Let say you bet Player B who is a receiver to win game 3 with the odds of @3.50 . Player B might go up 40-15 or 40-30 then once he reached that 40 points mark , he will definetely looking for Landing Permission from the agent who control the venue. If the agent signalled " hey you cannot land now" . Then the very next thing happens is a "planted" ACE , whereby this receiver just allows the server to hit without returning, or skying the return.Then he may play again until reach another Advantage and look for Landing Permissions from the agent. this will go on and on . If the players didnt act according to the agent, the agent can ask the sportsbook who received the bet to file complaint to the authorities that this player have links with the gambler . So this is the reasons players from lower level taking small $$ from agents and follow their instructions. This is why whenever you bet on ITF / Challenger matches especially on invididual games betting , you will always lose money even you are up 40-0 ..