Most times people may not have that intention to cheat or having multiple accounts, but due to this IP restriction lot of people wouldn't know about that the some casinos are that sensible to detect people from signing up twice using same IP. Like that days again, I told a friend about a cryptocurrency gambling site and was willing to sign up but guess what? Was having network challenge and asked whether if I could help give access to my network and I refused because I knew the implications about the gambling site that whenever two people signed up using same ip there is punishment for them.
With this casino could keep losing customers, instead it's important to follow the advise Charles-Tim gave that whenever two account are found using same ip it's important to merged them instead of banning them.
To further elaborate this, is whenever account is merged it is important to automatically set withdrawals only from one account while the account could be set as void instead of banning or restricting them entirely.
+1 karma for you @Charles-Tim