Your logic sounds like, if there is a chance to cheat, it should be allowed 
(just kidding)
My logic says it shouldn't be called cheating. Arbitrage betting isn't against the law, it's legal. Arbitrage trading keeps prices between exchanges very close to each other, while the exchanges still earn from each trade. Arbitrage betting should be no different. (just kidding)Example:
Imagine a boxing match between two boxers, John and Paul.
One bookmaker offers 2/1 odds for John to win, while another offers 2.5/1 odds for Paul.
A gambler calculates how much to bet on each outcome to ensure a profit, no matter who wins.
They decide to bet $100 on John and $80.89 on Paul, for a total stake of $180.89.
If John wins, the gambler earns $200, making a $19.11 profit.
If Paul wins, they earn $202.22, resulting in a profit of $21.33.
At these odds, I'd bet $100 on John and $100 on Paul too. If John wins, I profit $0, but if Paul wins, I earn $50. If a casino doesn't like that, then don't offer those odds!One bookmaker offers 2/1 odds for John to win, while another offers 2.5/1 odds for Paul.
A gambler calculates how much to bet on each outcome to ensure a profit, no matter who wins.
They decide to bet $100 on John and $80.89 on Paul, for a total stake of $180.89.
If John wins, the gambler earns $200, making a $19.11 profit.
If Paul wins, they earn $202.22, resulting in a profit of $21.33.
What you call "cheating", I call math. Gamblers gamble because they all think they can beat the odds. And if someone actually does that, the casino doesn't want to pay.