In my opinion, playing with fake money in an app and playing in demo mode, again, basically with fake money, doesn't bring you the satisfaction most gamblers are looking for. It may bring you some bad feelings even. Like once I won with a really huge multiplier playing in demo mode , and I was sad about not playing with real money at the time.
Don't want to lose a lot of money on gambling? Make the smallest bets possible. You can spin it with just one cent on some slots. That's a better solution, imo.
I also agree that it does not bring satisfaction to a gambler that is goal is to earn profit from winning. Since only a real money can make this kind of gambler satisfied. But after thinking deeply, there are people who play gambling for entertainment regardless of the outcome of the bet. Meaning they are spending real money just to watch the reel move. So an alternative way of gambling with fun tokens can greatly help this kind of gambler to save money. As the other thread stated,
People are not only gambling to win but they are buying entertainment so these people can just use these apps (stated on the OP) to save a lot of real money.