It's not obvious to any new gambler and it's a good reminder. Most bookmakers make tiny margins on individual bets and make most of their money from multi-bets, which should tell you that the odds are certainly not in the favor of the player in that situation. People are very poor at judging mathematical odds once the calculations start getting complicated, especially the average person trying to calculate a 5 string set of wins - you can guarantee that most people placing a bet will only see the huge multiplier and think they're making a wise choice. The odds against you actually go up exponentially the more games you add but the payout doesn't change to match it.