The point is, Lacrymas, that it's a really easy change, since you already have hireling functionality. The reason it's not included, I assume, is because writers/designers don't want to give that control over to the player.
There's two reasons I think this makes no sense:
1) Beyond everything else, what I love about RPGs is character customization. Having to choose between freedom to play with the system that the designers spent so much time working on (hirelings) or narrative content seems arbitrary to me, since:
2) The only functional difference between allowing me to control companion builds and playing with hirelings is that hirelings don't have narrative content. I would like to enjoy both parts of this great content the designers made, so I can't, and the reason is that someone is afraid I might not be able to handle playing with a version of Aloth who's a Cipher instead of Mage mechanically.
It's easy to implement and hurts no one. I don't get why Sawyer of all people is lagging behind Larian of all studios here - after all, he's the biggest proponent of gamism in a Lead Designer seat currently. For christ sakes, this is the man who defended Might Wizards, yet I can't play in this sandbox system he made out of fear I'll lose something narratively if Aloth has 18 Might? Why then provide the alternative of hirelings foregoing narrative content altogether?
It doesn't make sense.