Internet casino gambling is legal in only a handful of states, but the industry is convinced it is the future of betting, even as some worry about cannibalizing physical casinos. Speaking last week at the SBC Summit North America, a major gambling industry conference, industry executives acknowledged the difficulty they’ve had in expanding the legalization of online casino games. Yet they remain certain that, like many other industries, the future of gambling is online. “Once you get to millennials, people are comfortable basically running their entire life off their cell phone,” said Elizabet…