There is also the psychological damage. A Bronze Age society suddenly confronting interstellar civilization with technologies that look like magic, and science that they don’t even have the building blocks of the building blocks yet-will disorient, confuse, stun, upset, and shock the culture in question. “Oh wait the sun isn’t a deity that provides warmth to the crops, it’s just a big ball of fire”, “our world isn’t a great table at the gods’ footstool”-the effects of shattering the beliefs of the population, are bad enough there are also inter generational affects, and the obvious fact you have to bring the culture up to speed on science and technology is just a massive pain to deal with.
It is actually traumatic, and will cause no small amount of social crisis, spiritual crisis, a crisis of political authority, among other things.
Obviously the federation doesn’t want civilizations to remain in this state forever-they believe that scientific and technical progress should occur organically, that is without external interference beyond the world itself. That allows the society to change and grow with it, and yes that means wars, as ideas and values are spread, fought over, territories unified, laws codified, etc…
This is “natural” in the sense it happens without a more powerful artificial presence affecting it. It is the world and civilization as a distinct entity or system evolving on its own.
Is there are a lot of suffering in this process? Yes. And one can make an argument that “natural development of society is outweighed by preventing suffering”-which fine, make that argument. But then you are responsible for that civilization’s uplifting, and shepherding them to the stars.
And that is both a massive investment and extremely presumptuous and paternalistic.