Security doesn't need to be 100% effective to add value. The more hoops we make scammers jump through, the fewer people will end up getting scammed.

I know angle grinders exist. I still lock up my bike.

Scams have absolutely nothing to do with anything relevant. Scams happen regardless of whether software is installed in the first place. Social engineering is what most scams are based on. Refusing me banking access because I want to use my phone as a computer brings extra security to nobody.