Why not put an audible variometer in every glider?

In article Martin Gregorie writes:
On Mon, 03 Jun 2013 08:12:00 -0700, son_of_flubber wrote:

"CFI-Gs largely hold sway over how we equip our trainers. Many CFI-Gs
just want the student to pass the PTS ASAP, and basic skill with a
audible variometer is not part of the PTS."

If a student isn't taught the elements of soaring during basic glider
training, why would anybody expect him to stick around for long? I should
think that flying a glider without having the necessary soaring skills
would get boring rather fast.

But, why do you need an audio vario to do that?

I learned to soar in a pair of gliders with mechanical varios. One of
them did not have a TE probe. For a while, early on, I considered getting
one of the hang-gliding audio-only varios, but eventually abandoned that
idea.

Much later, when I was out in a higher performance glider, we decided to
turn the volume down on that annoying thing.

Alan