Learning from teachers is a skill that can be learned, and taught.

Being unable to learn from others or collaborate with others will vastly limit what gifted children can accomplish in life. Not teaching those skills as skills sets gifted children up for failure in college and the workplace.

There's also other skills that are very often difficult for "gifted" kids to learn: rejection sensitivity disorder, for example, is often comorbid. Somatic exercises, learning to pay attention to our bodies and not just our intellect. Note taking. Slicing problems into small pieces it is okay to fail. All of these are things conventional education assumes kids will pick up on their own.

We have actual studies on the results of unschooling gifted kids, and the outcomes are not good. It is much better if they can be coached on skills they don't have, even when those are skills other people acquire passively without having to be taught.

It doesn't necessarily take "more" resources to educate gifted children: it takes differentiated resources. "Your brain works differently, so this classroom works better for you" is just as true for learning disabilities as it is for "gifted" students.