We keep our prescription meds in other parts of the house - that's mostly because it's easier to refill the pill holders when they are in a box to pull out.
But it is true there are a lot of people that will look in a medicine cabinet with no intention of stealing, just being snoopy. I was always taught to mind my own business. With my luck, if I did look into someone's cabinet (without permission) it would collapse like the one in the commercial. One time I was visiting a friend and I needed an aspirin and she told me it was in the medicine cabinet and help myself. I was so uncomfortable doing it - but she thought it was a normal thing.