HYIP and gambling is the same as each other because they contain high risk. But, HYIP is more terrible than gambling because it is not good, it is created by scammers and people will 100% lose their money in HYIP. Gambling is somehow better than hyip. But there is always the house edge and therefore, there will be a chance that you will lose all of your money. Therefore, I think that provably fair games are only for entertaining purposes
I believe they are similar. On long term both are unprofitable, both involves high risk and some luck. HYIPs steal you, that is true, but you don't know when this will happen and at gambling you don't know when the long loss streak will happen, the only thing we know is that sooner or later the long loss streak happens and the HYIPs steal you. That is a similarity.
Gambling is better because it's a game and not only an "investment", so as you said, it's possible to have some fun (entertainment purposes).