I've never had a reason to believe they didn't work. Last season a friend and me were sitting in a blind in a small clearing when a tom, 2-3 jakes and 3-6 hens made their ways out from the right. I'm sitting on the right and didn't have my side of the blind zipped down far enough, so my friend has a perfect shot and I can only see them out of my side window. We had 2 hens and an aggresive jake decoy out, before you know it, the turkeys walked straight back into the woods, so we blew it!
I used the gun barrel to zip down the window almost fully and in desperation, I asked for his gobbler tube, I immediately starting cutting and shaking the gobbler tube and the turkeys lit up inside the woods, double and triple hammering. After about a minute, a hen showed her beak, followed by the tom and 2 jakes. BOOM double header. I ended up with a jake and he shot a the 5 year old tom.