Beautiful girls are exist in casinos to distract gamblers mind. Gamblers will act like they are a pro gambler just to impress the girls. Some people can control their feelings when surrounded by beautiful girls, but most do not.
That is actually the function of a beautiful woman in addition to the gambler is to spoil the concentration of gamblers. Some gamblers will become more confident if there are beautiful women beside them, but that does not mean it will increase their luck. And most gamblers even feel nervous and chaotic if they gamble in addition to beautiful women.