You can invest in the platform that have their own tokens since it's something that you will use for gambling it's properly okay, because i believe with their token they are also promoting the token to be well known, i know that other people will be understanding it from different ways which is not quite right, the gamblling sites Owns the token.
We aren't going to invest directly in the platform, that's a different thing already but there are gambling sites that work's like that. The feature is called bankroll investing. The OP is only asking about those casino coins. The OP doesn't also want to play gambling or use the casino tokens for gambling but he only want to hold it like a typical investment asset.
I only know a few casinos which has their own tokens, I think that is because they promote their coin properly. They also want it to be more known other than their casino. This is the importance of doing a promotion. It helps people to be aware about the company's product. This is one the thing that we must look at before we decide to invest.
