Users don’t read warnings. Most scams capitalise on urgency. When given more time to stop and think something through, it often becomes obvious what’s happening.
Why should that be a concern to a phone OS provider? A concern so important that they are willing to cripple couple billions of devices.
Then, generally, "software is just a tool like a knife" doesn't hold because software today is more a service than a tangible good. Companies continue to update the programs and things can happen in the cloud with limited user control.