> its pretty common that whatever you've locked up to (sign post, bike rack, parking meter, handrail, etc) is a lower grade of steel than the ultra-hard stuff on the shackle

Way back in highschool this always used to baffle me. You'd get kids spending $50+ on super fancy locks for their lockers, but all these locks equally were fastened to the locker with a flimsy little hasp that you could cut with a pair of tin snips, assuming you didn't just bend back the door of the locker itself.