I do not see any good reason for them blocking multiple accounts in casino gambling by the casino platform because it has no negative effect to the platform. As long as those accounts do not go against the rules of the casino platform. They need more users and that is also part of getting new users into the system. The reason for banning multiple account in the Casino platform should be that they either violate the platform rules or cheat other users int he platform.
Majority of people that creates multiple account in a casino are doing it to cheat the system and not because they are hoping on getting a different experience from the account. Some of them create it to cheat in tournaments and also to abuse several NDBs - we have seen several cases of accounts being created so that they could get bonus and then tip their main account and they continue doing it till their account gets the minimum withdrawal amount.
I remember when I created a double account at bcgame to test out the self exclusion system and then got reminded by a user here in Bitcointalk that I should let them know about my other account and have them disable it to prevent future problems with the site.