His argument is that the rich people gambling do not have to pack a lot of odds as in parlay bet to accumulate a high odd size that will give a satisfying potential win. The rich has the money to risk huge amount to a single game for instance 2 odds staked with $1 million to win $2 millions,  but the poor staking with $100 to win  $2 million has to pick multiple legs to accumulate odds to get such potential win.  It hence decreases the gambling winning chance whilst the rich gambler chance remains increased.