Pure and simply, the community has become too wound up about balance and expedience.
Can't have a pet monster or follower trivialize an encounter. Extra followers skew carefully crafted fights, making them less "epic" - or "take too long" because of number of combatants. Why have 4-10 hp followers along if the party is delving into dungeons where one monster hit does twice that and won't miss the follower's lousy AC? What player is going to want to play second fiddle - or RP someone else's henchmen - when it could possibly detract from their spotlight?
If you lose a resource, it has to be able to be quickly retrieved, with minimal fuss or players won't use it. We don't balk about PCs getting ridiculous numbers of hit points, but if a pet/mount/familiar gets equal attention, it's unbalancing. If it does drop to 0, the fiction must absolutely be it dies, rather than just pulling back out of that particular encounter. Who wants to take horses and tie them up outside a dungeon where they aren't used, you might not come back the same way or someone's scappered off with them while you were cleaning the dungeon out? And if you do, poke-ball it like the Paladin's mount or familiar so you don't lose it. And why have a mount or beast of burden, if you aren't using encumbrance in the first place? Why would you need a mount when you'll get there anyway on foot in the same amount of narrative time?
"Name Level" used to be a place where you could really change the tone for those players who wanted to go the leadership route. Instead of doing Avenger-Level group threats, they could strike out on "lone" adventures with their own retainers, oversee growing and guiding their own guilds, groups or whatnot (likely only getting directly involved at a critical point), lead wars or raids or tell a vastly different sort of story more akin to Braveheart than Fantastic Four. Y'now, the sort of things that would fit for Battlesystem, Basic's Mass Combat System, Birthright and things like that. All of that got taken out of the game - not just gutted, but removed.