Be careful, "always" is a long time. What about when you're the only instructor, and there are 30 kids with brand new ARFS waiting in line at 8:30 Saturday am for their "free" lesson? What about when they start complaining that they paid their club and AMA dues, now what kind of service is this that they wait in line and only get one flight in a week? Now one Dad steps out of line and asks you if he can get some paid instruction, that he would be gladly willing to pay $20/hour (chump change compared to all the other lessons the kid takes) just so he doesn't have to wait in that damn line.

Then, at the end of the year, you notice that of all those folks you trained, less than 5% have re-upped and joined the club. Where are the future volunteer instructors going to come from? You trained 100 people. 95 have disappeared. Of those 5, how many want to be volunteer instructors? Yet next year, you have another 30 newbies to train, and your pool of instructors isn't growing too quickly.

This obviously doesn't describe your field, or anything you can imagine. But believe it or not, it's not that far fetched. Very dedicated, generous helpful people are looking at scenarios like this today, and that doesn't even count all the people who want to learn, but who take one look at that line and decide to do something else.