Do you really think i'm gonna take a sealed box without checking its contents first ?
I never buy anything locally without examining it first and making sure it's fully working and in good condition so no pixies for me, thanks...
Sure, you might, but a lot of people are more naive, just take the thing and walk off.
But testing the thing is dangerous as well. You are meeting a stranger, and have to go together to his gaff or your gaff to test the thing, its not like you can test it in the park