Maybe you are not familiar on how Fortunejack, Primedice(Stake) and Bitsler start there casino from a normal dice game to a Big Casino with sportsbetting right now. How long have you been in the forum for not not noticing the history of this giant Casino progress here. I believe the only Casino that I know that start on Sportsbetting is sportsbet.io but they are from a huge company so its understandable how they can easily upgrade there Casino. 
That's true, they I played on those sites before with only casino games. It didn't happen in just a month or quickly it all goes through a process and I don't think the SandboxCasino will come to that let's just support what they have as of now, so far they're doing good with the NFT feature I hope they can add more regarding the NFT.
Like Duelbits as they started in Dueling and then now? a fast growing casino already .