Well if you did the same with a portable redstone signalling item (yes mostly mods do this but there is a reason why, even Modded Storage systems with wireless access are useful for a reason) would it be useless then, I'd say a Whistle is a great idea if you want control of something and don't want to go to it just to interact with 60 different mobs to tell them to sit (if you bring all of them with you yeah it's a bit much or they don't behave for whatever reason it's useful for those reasons yes, who cares if a certain percentage of people use it. I don't use enchantments or potions will Mojang scrap them because I don't use them, no and those are a big part of the game but it's my way of playing compared to others) or in the redstone case want to go home just to stop a contraption.
I support this suggestion and I could come up with similar situations as to why it's a good idea besides the Redstone one. And yes I don't use wolves, and I rarely use Horses but I do from time to time but I can at least see reason in why an idea like this would be great. If not then a mod probably does or should exist that does this.