The announcement that Marksmanship would be the pet-less Hunter spec was met with... well, let's call it controversy. From a bird's eye view, it kind of made sense: each Hunter spec would have its defining characteristic - you'd have the petless spec, the melee spec, and the "classic" spec.
The Marksmanship specialization always had less of a wilderness survival vibe, and always seemed like the most potent "military marksman" fantasy, something that the changes in Legion aimed to focus on. The popularity of the Lone Wolf talent in Warlords of Draenor seemed to suggest that people were willing to forgo their pets in favor of more damage. Given that the "dead-zone" has long since died, and Hunters no longer have a minimum range to use their primary ranged weapons (which are, of course, now their only weapons,) the loss of a pet that can tank for you while you solo and contribute little chunk of dps when grouped was not quite as class-shattering as it might have been in WoW's earlier days.
But pets are also one of the most unique things that Hunters have. While Warlocks have always had Demon minions and there are other specs like Unholy Death Knights and Frost Mages who have their own permanent pets, Hunters are the only ones who get to go out into the world, find a beast, and tame it to be their best friend. It's a level of personal expression that the other classes don't get.
Now, some people may have decided that they'll just go Beast Mastery (my best friend's Horde main is a Marks Hunter who adores his pet pig Sid, and he's been resigned to this.) Now I love Beast Mastery, but its focus is so firmly on pets that you do sometimes start to wonder if it even matters if your actual character is any good of a shot. Marksmanship Hunters are quick-draw snipers, and that's a valid fantasy. Beast Masters have a near-mystical connection to the pets, and Survival's fantasy is that of a loner who prefers to be out in the wilderness at all times. There's no reason you can't be a metropolitan sniper who has a loyal hound/cat/scorpion.
Anyway, I'm fully in favor of this change, especially given that they're going to keep the current iteration of Lone Wolf (minus the buffs, of course, because all longterm buffs are gone in Legion) but moved way down to level 15 so that if you wish, you can go petless very early in your Hunting career. Very little is lost here, and I know that tons of Marksmanship Hunters will breathe a sigh of relief.
Now, if they can only release a version of the Marks artifact weapon that acts like a gun...