Are you sure of that? I hear often of people putting traps out, and not catching anything. I think that's why traps are changing - because mice/rats learn to avoid them.
You only think all the mice are dumb because the smart ones avoid the traps or find ways to get the goods without setting it off while the dumb ones get themselves killed. Well, I wouldn't call them dumb, just..unaware. I can't think of a better term.