Thats changed now and there are regulations about having posters up everywhere. So they don't have to ask the questions but some old hands on checkin still run through them.
As for the not spotting, its perfectly normal for stuff not to be seen. You get pax coming up and handing over all sorts of stuff which you are suprised they got through. The two that spring to mind was a set of hydrometers which were glass things with serious amounts of mercury in them (they didn't travel and there was mucho issues about) in an antique box. I think they went by royal mail in the end which I had serious issues with when I found out because it would have written off the airframe if they had broken and it completely took the mick out of DAG regs.
And a couple of sets of shefs pro kitchen knife rolls which hannibal lecture would have been proud of. The chefs in question said they always took them in hand luggage and handed them to the crew when they got to the aircraft. And they certainly didn't come across as if they were telling fibs.
Its one of the reasons why crew gets so irrate when we get reamed because we know what does get through and whats airside anyway.