Because an app store will always be a bazaar. No one is doing full human code review on apps.

To pretend otherwise is insane. (Even by appealing to app store monopolies or fees, which are immaterial to due diligence responsibility here)

This wasn't a case of the lady giving $5M to Google for fake crypto.

It was more like Google selling her a phone, then her dialing one of the preset numbers on that phone and getting scammed.