Any bike worth its salt can be stolen or stripped or damaged. I used to repossess bikes - never had any trouble. Nobody argues with a determined fellow carrying bolt cutters and other tools.
So I never leave my bike locked. If I have to go in a store for a moment I flick the quick releases open and jamb a twig to lock a brake. Or I take the bike in.
Never had one stolen this way.
Otherwise it's a risk.