Probably makes the admin easier.
I never did it, for the usual reason of it not being made clear what it was or why we'd want to do it, and by the time I found out by osmosis it was too late. Same way I never learned to play a musical instrument[1]. It being mandatory would at least avoid that problem, but so would actually explaining things to the kids, rather than assuming they know what you know.
Agree about the financial implications, unless some sort of bursary or something is available.
[1] "Those who want to learn the recorder meet in room foo at breaktime" != "Those without pushy parents who don't want to miss out on the basis of formal musical education meet in room foo at breaktime."