Its true that most gambling sites won't survive even for months but many new gambling sites represents that we are getting more competition and more quality of service while gambling but we should not consider it will increase our chance of living with gambling.
That is for the business owner who operates their gambling site. Maybe they are not use gambling as a profession, but they are a business person in the gambling section. But for the gamblers, I think that it is difficult to live out of gambling since gambling is one exciting thing that people want to play. Maybe for the gambler who can master one or two types of gambling can live from gambling and they are making money for buying something to their daily life.
Besides that, gambler and gambling owner is different so we cannot say that the gambling owner is a profession like a gambler.