I have only bought three new guns in my young life. The years I spent as an LEO I never bought a new gun. I have also NEVER bought a lemon.Used guns, unless you know the seller, are a crapshoot at best. A used gun may be broken down or a lemon, with a new gun you get to break it in yourself and you know that it's well maintained.
I am not sure about others, but if I had a lemon I would not sell without full disclosure. As for as I can tell most responsible gun owners are of the same opinion.