What’s the alternative? The bank sending out a debit card to anyone who calls up and says “I’m @kristov, trust me…”

Are you under the impression that this wasn't a solved problem for the half-century before "apps?"

Yes, there was some tiny fraction of fraud, but it's not like adding all these layers upon layers of technology has fixed anything. The difference is that instead of getting ripped off by one of the people in your own town, anyone anywhere on the planet can rip you off now.