I think it's more like, "you don't need a ground to air defense system in your backyard unless there lies a buried nuclear missile".

Also, a plumber would probably invest in mechanic arms to prevent possible injury when working before it comes to preventing physical access to his/her computer.

In short, it's a question of effort and priorities.

A default setting change protects me from black hats walking around with special cables in Starbucks? Yeah, sure, why not. Me having to carry my ultrabook in a locked steel case? Not so much.