If you don't like Bitcoin, you could always just get an address and if you get tipped, sell immediately. I don't see how this is any different than an app with "gems" you can buy and re-sell back to the app. Some games like Entropia[0] have a fixed exchange rate with the dollar, allowing you to "cash out" of the game, if holding game currency isn't your thing.
It's just game currency essentially for the social app. When I think about it like that, it makes me less nervous.
[0] https://account.entropiauniverse.com/account/deposits/#:~:te....