It's only difficult because computers are digital devices and all the "hard" things for computers/robots to do aren't done in hardware. Trying to have a single CPU do all of the things a robot needs to do is asinine.

Making a robot hand pick up an egg and a cup of coffee and turn a wrench isn't difficult provided that you build in similar feedback loops and low-level "firmware" that the brain does for us, unconsciously.

But if you did that it would take tens of kilowatts to run a halfway decent robot. And that's clearly ridiculous! So nobody does it.