A rich person may post how he/she won millions through a game but he/she will never tell or show the times he lost before the winning and the huge fund wasted along the line.
Gambling is for all, just as you've said already, this is not what the rich only have the right to enjoy doing because they have the money to use for it, base on my own understanding, i think the average people gambles most because they have the time and money to use for gambling, we may class the rich as people who sone of them don't even have time for gambling just the way other people do, we all have equal chances for winning when we are gambling and none is more favourable than the other between the poor gamblers and the rich ones, everyone is doing the same, what makes the difference is in what we know and how we have the understanding in what we do while gambling.
Every individual who doesn't understand the rules and regulations of gambling has already lost the game before he/she plays.
Having said that, despite the busy level of the rich, their enthusiasm level for gambling is what will determine how they find time to gamble and the rich are always more favorable by casinos than the poor due to the casino loyalty program which is always based on each players bet history fund.
Of course from most gamblers it is clear as you said that casinos prefer rich people because they have more power in terms of allocating money to bet compared to poor people who only bring a small amount of funds, but in terms of service and game probabilities I think everything is the same whether you are rich or miskins.