If offline casinos implement such a system, it will really be wonderful. And it will be really beneficial for the casino as with all the winnings, if they hold it long term, the profit value increases automatically as the price rises of crypto. Hence, it is really something that should be implemented. I think Japan might have some offline casinos that accept crypto.
Right now most off line casinos do not see the need to accept bitcoin, we need to be realistic, how many gamblers do you think have asked those casinos if they could let them play with their bitcoin? In fact years ago I asked that question to a casino manager and he did not even knew what bitcoin was, then i discovered any chance of bitcoin being adopted by any casino is almost zero in my country.
However if bitcoin begins to become more popular around the world then you will see bitcoin being adopted by all kind of business including casinos.