How to withdraw with Bitcoins? Also, why are casinos doing this?

Honestly, I also tried to play with some bitcoins cause I thought it would be interesting and maybe I would win more, but whatever, I stumbled myself with the same problem as you. Most of the times, you should have a wallet like outside the casino you are playing with and when you make a withdrawal, the casino is supposed to ask for the address of that wallet if that makes sense. idk how to describe to you how to make one, but this would be the main thing: to have a bitcoin wallet first (if you make one, do some proper research on that wallet so you don't get scammed or something :D) 

As for why casinos do that, this is what I found online "it  can enhanced security, privacy, and reduced transaction fees" which could be beneficial for both the player and the casino. It makes sense cause bitcoin is mostly secure when it comes to personal details and such. I didn't stick to much to playing with bitcoin on casinos online cause it's not really my thing, but my experiences tell me that it is safe.

 Casino betting uses Cryptocurrencies because players with Cryptocurrencies are available worldwide and can make a deposit regardless of the bank and can also remain anonymous, unlike a bank transfer. To transfer, you need to have a crypto wallet, and in most cases, you can also transfer to a crypto exchange. 

Of course they prefer Bitcoin , if btc is going up so are their profits ! Pay them 50 to play , tmw fifty btc might be worth 62 ! In addition probably less chargebacks from CC and btc not fdic INS so if they wanna just take it , who ya gonna call....not ghost busters !