I lived in a period without debit and credit cards. You dropped your cash it was gone. I'm not sure not having a reversal transaction is the killer missing feature.
I know what life is like with the existing feature of getting thousands of stolen dollars back by relying on the banking (and/or legal) system. I won't willingly adopt a system without it.
Most Android phones stop receiving security updates after two years or less.
Can someone hack an exchange or your bank account login/password or your bank or worse setup for an account under your name no phone needed?
There's plenty of malware that looks for unsecured Bitcoin wallets on machines it infects, or masquerades as legitimate wallet software.
If you have root, you just need to wait until the user unlocks their wallet, or if you're lucky, their wallets don't have passwords.
With bitcoin it's medieval ages at best.
If you don't know the other person then cash or bitcoin it wouldn't matter.
If you drop your cash it's gone. If you drop your bitcoin wallet and you backed it up you still have your bitcoin..