fighting over the little money that most younger gamers have to spend
That's where the money is tho. Presents, pocket money, paychecks that don't need to go to rent and utilities. Everything I had I put into games when I was a kid. Sure I do have more money now, but I also have exponentially more bills to pay. My dad is retired and is pirating left and right cuz he can't afford gaming. Also, kids don't inform themselves before buying. They're much more prone to ads, social pressure, etc... Adults don't care if a game is 5 years old, which incidentally can be bought for a fraction of the initial price.

Money transfer platforms are even worse than chat apps in terms of how acceptance dictates usefulness. You might convince a couple of friends to use xmpp instead of whatsapp. But its near impossible to get major outlets to integrate new payment methods. Especially if that platform advocates privacy and therefore doesn't offer a return on invest based on user data. I don't think we're gonna see true alternatives without government regulation, and even then...