Because human brains are giant three-dimensional processors containing billions of neurons (each with computationally complex behaviors), each one performing computations >3 orders of magnitude more efficiently than transistors do, to train an intelligence with trillions of connections in real time, while being attached to incredibly sophisticated sensors and manipulators.

And despite all that, humans are still just made of dirt.

Even if we can get silicon to do some of these tricks, that'd require multiple breakthroughs, and it wouldn't be cost-competitive with humans for quite a while.

I would even think it's possible that building brain-equivalent structures that consume the same power, and can do all the stuff for the same amount of resources, is a so far out science fiction proposition, that we can't even give a prediction as to when it will happen, and for practical purposes, biological intelligences will have an insurmountable advantage for even the furthest foreseeable future once you consider the economics of humans vs machines.