My take on this is that music students need experience (and success!) in public performance, just as they need experience and success in counting the beats and learning correct fingering. If former students choose not to continue public performance after they stop studying, that's up to them - in the same way that those who are no longer students sometimes choose to take a little break from scale practice.
I don't think a teacher can get around this by substituting other things. I think public performance itself is what counts, not just putting in an additional experience of some kind. Without performance experience, one of the main parts of music education is gone.
I'm in total agreement with you.
It reminds me of a conversation many, many years ago. Parents to little Johnny while visiting friends - "Play something for everyone."
Johnny replies, "Sorry, I can't; I don't have my music." (I'll leave out the repetitions, pleas, anguish, embarrassed comments, etc.)
What it boils down to is: if you cannot play something on command, can you really play the piano (violin, clarinet, etc.)? I suspect most people would conclude you really cannot play.
That is why I have my students maintain repertoire, and it's why we have monthly performance class at the studio, and why students perform publicly 3 or more times a year.
In 30 years, I've lost one student because of this practice, and she was actually a transfer student, and I suspect that there were other issues involved beyond the memory work required.
BTW, yesterday was our monthly performance class, and students averaged performing 4 pieces each. They did well, and I feel they provided each other moral support to boot.
And probably the pizza afterwords added some comfort to the event.
"Those who dare to teach must never cease to learn." -- Richard Henry Dann
Full-time Private Piano Teacher offering Piano Lessons in Olympia, WA. www.mypianoteacher.com
Certified by the American College of Musicians; member NGPT, MTNA, WSMTA, OMTA