The problem with most gamblers is that they only place importance or emphasize more on the importance of walking away when in a losing streak, yet do not realise that it's also very important to know when to walk away even while on a winning spree.
You shouldn't be surprised about this because such individual who keeps losing and refuse to back off is already addicted to the game. One thing about addicts is that they know they're spending a lot on gambling and might not be profiting from it but they don't know how to quit or they can't quit rather cause they've become used to the act, to them it's like a hobby, something they can't do without.
Such individuals need help, maybe from family or a therapist else they'll keep doing it on a regular and whether they keep losing is not an issue for them cause they just have this believe of being lucky someday. It's almost very hard to convince a gambling addict to quit it totally it takes a gradual process with regular therapy to help addicted gamblers quit.