Not only was it easy to enforce but it was selected because it was a
desireable enough reward that people would put in the training to get it.

Most rewards in the real world have little relationship to the work
requested. You see it in the home too. Kid asks, "Dad can I borrow the
car?" Parent replies, "After you mow the front & back lawn and run the
edger." There is absolutely no relationship between the two activities.
The kid gets a highly desired reward for work that he/she probably doesn't
care to do but does it anyway to get the reward.

SOme kids and others may decide that the reward is not worth the trouble
and time needed to do the required chore. If it's an option, vs having
to take some stupid class in HS or college because some curriculum
committee decided that it was necessary. Not graduating is not
a desirable option. I had to take 3 years of Spanish class in HS, but
as I don't own a landscaping company, it was a waste of time. :-)
Japanese would have been a better choice, but they didn't have it.
Some kids may feel that they are saddled with non-optional requirements
may decide to edit out of their lives any optional requirements and
forgo the ham license or similar.