L'Aviateur.
I sometimes carry a bag for a friend, who has a great deal of photography equipment, so I help him out with some of the carry on. Like you, my answer is 'No' for precisely the same reasons as you gave. Inevitably, the bag is then emptied and checked. So it's a tiny inconvenience, but I like you, prefer not to lie.
PT. It's asked everytime I fly, and that's reasonably frequently!!