Why do IP phone manufacturers eliminate sidetone?

Side tone is where you can hear yourself in the handset of the phone—it’s actually a side-effect of analog phones. Earlier IP phones I had been using had pretty decent sidetone. Snom, when they updated to version 7, specifically had in their changenotes that they were turning sidetone way down. (Not as a default, as the only way it could be).

The biggest problem here is that you take the fact that you can hear yourself as a cue to talk at that volume. You can actually trigger people to talk quieter by making the sidetone quieter. The lack of sidetone makes people subconsciously talk louder, which turns out to be a bit of a problem in our small offices.

We just switched our office to Aastra phones, and they have the same very-quiet sidetone.

Why would they do this?