This situation reminds me of a legal loophole to buy bitcoins using a poker site. Perhaps there are very favorable conditions for the purchase of bitcoins, so people can place their deposit on the site, play a few games and request a deposit withdrawal in bitcoins. Didn't you think so?
Did you mean depositing using fiats? That will be also included in some companies gambling sites in which you will be able to purchase bitcoin with fiat but it will only be good for people that are not concerned with privacy. I still like to make use of p2p ways and also noncustodial exchanges for bitcoin purchase. But if you are not privacy concerned, using credit card that the gambling site support is good.