Why would it? At the moment we can't even emulate a fly at the AGI level. So our AGI now is "much slower" than 1 human, never mind "7 billion human brains put together".

And it doesn't "self improve" at all.

We might never be able to emulate a human brain good enough with our technology and resources. Including tomorrow's technology, either for the same reason we will never get 0.1 nanometer chips or sub-zero roundtrip latency around the earth: the laws of physics, or for the reason that it's too complex (and there's no signed contract with the universe that humans will eventually be able to handle any complexity level in their technology. We might hit several hard problems where we don't have better ideas, or better concepts/inventions are far beyond our grasp).

It’s not even speed. Most humans waste most of their days on minutiae. We spend a lot of time entertaining and amusing ourselves. Watch everyone trying to be clever in a Reddit thread, for example; a complete waste of time.

We’re also full of biases.

https://jamesclear.com/great-speeches/psychology-of-human-mi...

Humans also die, and so have to give birth to new people and train them over and over again to maintain and develop social and economical structures. Artificial brains don't have to die, they can be also cheaply duplicated, and their old versions can be stored and used later if need be.

humans usually die after several decades. They do take decades to train. It would be beneficial when we live to 110 and work to 100. At any rate, we don’t do enough with our existing time.

When we focus time and effort on things like the Manhattan Project or the Apollo Program, we are able to accomplish a lot in a short time.