For me, gags have always been more about the aesthetics and less about how effective they are.
There's no doubt that a single strip of duct tape would be ineffective - even if it was super strong and you couldn't chew it off, it's still not going to be difficult to make a hell of a lot of noise through it. But the way I see it, there tends to be a trade off with effectiveness and attractiveness - wraparounds and multiple strips and huge amounts of mouth packing are all better at silencing, but I often think that they look a bit unattractive (although obviously, not everyone holds that opinion!). I prefer to use my imagination a little and put up with less effective gags if it means that they are more attractive to me

That being said, I do find it endlessly annoying when someone has been poorly gagged in a scene but makes absolutely no noise. No gag is THAT effective
