This is a great point I just came across in some of my notes, from I think the book Fearless Faith:
I’ve always wondered why we could be so quick to sacrifice our children to become missionaries but stand in the way of their becoming broadcast journalists, film and television actors, photographers, and painters. It’s almost as if we believe God is strong enough to take care of his own only as long as they stay within the safety of the Christian ghetto.
I’m all about missions and taking the gospel to unreached people groups. I think that, in addition to this, we also need to realize that the gospel also spreads through the vocations of all Christians, wherever they are (as long as we understand the proper relationship between faith and work — which most don’t!) — and that more Christians are needed in culture-shaping vocations.
In other words, the recovery of a robust doctrine of vocation is just as essential to the completion of the Great Commission as embracing the challenge of going to hard places to bring the gospel to those who have never heard.
(And, beyond that, as people come to faith through the vocations of every Christian, there will be more who in turn go to the unreached.)