I guess you never heard of 16 Psyche?

The best use case for material from asteroids is for making things for a space station or space travel not for terrestrial applications.

You don't have to go to the asteroid belt to find asteroids, some come very close to Earth, sometimes closer than the Moon.

If we have large colonies in space then I expect they will eventually use materials from asteroids.

Depending on events, this may never happen and no matter what it will be the distant future.

Just to let you know

"on April 15, 2029, an asteroid will swing past the Earth, just barely missing everything. The asteroid—nicknamed Apophis—will be as close as some of our satellites and only a few thousand miles away from the Earth’s atmosphere itself..........Apophis is huge. It’s over 1,000 feet across, meaning it will be big enough to see with the naked eye when it flies past us. Most asteroids that nearly hit us are only a few dozen feet across."

https://www.popularmechanics.com/space/solar-system/a27356198/asteroid-flyby-2029/#:~:text=May%203%2C%202019%20A%20decade%20from%20now%2C%20on,thousand%20miles%20away%20from%20the%20Earth%E2%80%99s%20atmosphere%20itself.

TEK