That may be true for slots (although even that mundane aspect could be made much better with some VR, eg being able to see that someone is sitting next to you and talk openly with them; or to be able to sit next to a friend, and see that they just hit a jackpot), but there is a drastic entertainment difference when it comes to visually perceiving that you're sitting at a poker or blackjack table with other people, and being able to look around. Hitting that sweet spot where your brain forgets that you're not actually there, that sense of tension at the table when the stakes are high.
It's all about atmosphere and entertainment. That's why Vegas exists. A very small fraction of the Vegas crowd are real gamblers. And I think it's why VR gambling will go far upscale from the texas hold'em on our smart phones. It'll be about charging for an experience.