Meaning, they don’t cash out their profits right away, they reinvest it as additional bankroll.
Reinvest in gambling? I'd surely not associate that term with betting, i don't know who these experts are or if there are experts in gambling like you say, but i am
auresure they do not have any crazy advantage over others like
toyyou make it seem. You could go crazy about gambling, try to figure out all the tiny nuances, find crazy strategies to beat the casino, etc, that does not make you an expert, treating gambling like an investment does more harm than good and you'd be lucky not to become an addict.