While I acknowledge that this, for most, would be taking it to an extreme, it’s not unheard of cases where some players have upwards of 30, 40, or even 50 hunter alts on their account. Regardless of what the currently highest number of pets a single player has tamed, across all of their hunter alts, you can take a look at the theoretical potential numbers.
If someone were to have 50 hunter alts, with a total of 205 pets on each hunter(the max per character), that would equate to over 10k pets in total. Imagine a shared stable, hosting more than 10k hunter pets. While I doubt that there are too many players who actually have that many pets in total, even if you lower that by 50%, that’s still over 5k pets.
Now imagine someone who have taken a certain pet out of their shared stables on one hunter but, at some point, they log on another hunter alt, and they want to use that same pet on that hunter. Then, they have to first figure out which of their hunter alts have already taken that pet out of the stable, they then have to relog to that hunter, put the pet back in the stables, and then log back to the other hunter, and then bring that pet out. And so on…
Again, most hunter players probably don’t even have more than a few percent of the maximum potential number of pets that you could have, if you happened to have that many hunter alts on your account. But even if you had just 3-5 hunter alts, and around 500 pets in total, as soon as you start thinking about swapping pets between your hunter alts, it could easily become a very negative experience, managing pets like this.
And we haven’t even gotten to talk about the absolute nightmare of trying to make this work from a programing POV. It’s not just about a quick fix to make all pets you have on your entire account appear(be displayed) in a commonly shared stable list, whenever you open the stables on one of your hunters.