Smart contracts don’t require you to have open source code and nobody can see the code either. Nobody can steal your stuff in this kind of environment.
Centralized servers means that you have a single point of attack. So when FBI/CIA agents bust down your door because some butt hurt bureaucrat made online monopoly money illegal you can let me know how it was such a good idea to take advantage of that immutable decentralized transaction service like ETH using your centralized servers. So much for those centralized servers eh, also welcome to being in jail for not having a money transferring license or whatever weird potential crap that might come down the line.
Honestly, when it comes to building in this space it makes far more sense to keep the games fully on chain and be anonymous if possible. This goes double depending on if you live in a country where the government is highly likely to try and tame the beast. Trumps lapdog Mnuchin made it very clear he does not want people even talking about bitcoin in the next 5 years.
A crypto based game with centralized servers is like a horse and carriage running with a diesel engine that can explode at any moment.