And it would take trillions to extract them while you can do it on earth for far less.
If there was profit in space mining people would be doing it right now.
Technology improves and becomes less expensive over time, so just because it seems like a profit losing endeavor today, does not mean it will stay that way tomorrow.
It also comes down to motivation. China had a massive fleet of ships a full century before the Age of Exploration that were superior to the caravel ships used by Columbus. But they saw no profit in it and had no need for more resources and land. The Europeans, on the other hand, were being squeezed out of the trade markets by powerful Muslim empires and were desperate to find ways to expand. They were willing to take greater risks. That is what you will need to see happen for a decent boost in the space age.