Why are you doing it? Dubbing started with games because it gave them an advantage over an undubbed bird when they fought them. That's why dubbing is written into the SOP for games even if they don't fight them, it is a tradition. I don't know what would happen if you tried to show a dubbed bird of another breed, I'd suspect a disqualification.
In really cold climates, dubbing could help protect a bird against frostbite. Or you might do it if the comb/wattles are damaged, either from frostbite or mechanical damage. I can see dubbing as an animal husbandry tool you could use in certain circumstances.
Bright red combs and wattles on hens are a signal to a rooster that the eggs need to be fertilized. So on a hen they play a part in behaviors. I don't know how important bright red comb and wattles are in a rooster to get the hens to accept him, it could play a part. I've read that frostbite to a rooster's comb could (not always but might) affect a his fertility. I don't know if dubbing could have an affect on fertility, I'd think probably not.
I don't see anything wrong with dubbing, under the right circumstances. It's just another tool of animal husbandry to have in your back pocket. But if you don't have a specific reason to use it, I don't see any reason to do it.