Whether the irreversibility of payments is a feature or a bug depends on the situation. Clearly reversible payments are a bad fit not only for scammers but also for things like Turing Pi.
More interestingly, they're also a bad fit for online payment systems like Paypal. Paypal steals its customers' money like this because it's profitable for them to do so; receiving money from money senders and then just keeping it is very profitable indeed. But they get away with doing it, despite the bad publicity, because there's no less-corrupt alternative their customers can switch to. The other Paypal-like companies born late last millennium all failed because the reversible payment infrastructure of the credit card and banking system stuck them with the bill for whatever scams and fraud were perpetrated on their platforms.