I'm not surprised that some casinos doesn't want to have an inside exchanger. It's risky and takes efforts.
Will make a very simple, even childish example, why I wouldn't implement an exchanger if I would be a casino owner

Two players came. Player A made a deposit of 0.01 btc, player B made a deposit of 0.01 btc, and both decided to exchange it to xrp for playing. At that time price I (casino) credited to their balances, let's say, 500 xrp each.
Player A had a nice run, made his balance to 3000 xrp and now wants to withdraw it. Where the heck I should get these from, if there weren't any xrp deposited? How much of each coin should I hold "just in case"?
While player B didn't win or lose much, and now wants to exchange his same 500 xrp back to btc and withdraw it. Problem is - prices changed, and now it's worth not 0.01 btc, but 0.012 btc. So I didn't earn from him any, but still need to pay extra from my own pocket?
Ofc sometimes it works in otherwise direction, but still - risk is too big.
Actually there's no risk with the casinos who will have an exchanger. The risk only comes if they're the one who's going to have their own exchange inside their casino but many of the casinos that has their own exchange insides are just integration of a 3rd party service.
They just have to connect their customers with an exchanger which is the 3rd party and it will do the job for those customers that want to exchange their deposits.