The problem with speakerphone-type systems is that there is a tradeoff to avoid feedback when it comes to noise in the background. If you are in the TCH and you hear a noisy background on the distant end, the system will likely cancel out or lower your volume in order to avoid feedback.

Feedback would occur if, for instance, your wife is speaking to you and her voice is picked up by the TCH microphone and transmitted back to her. So if there is any bit of noise that you can hear coming from the distant end, you may have sound quality issues.