I see the reason in
"It's not what you say, but how you say it."
That said, when I grew up, the common reply was:
Ich habe Dich nicht gehört.
The problem occures with any nonverbal gestures and verbal emphasis/ stressing/ intonation:
- you could mean there was an accustic problem.
- you could mean there was a problem in regard of content (you understand the words, but they make no sense to you)
- you could mean there was a problem in regard of situation (you understand the words, you understand a meaning of the sentence, they just don't fit into the circumstances)
- you could mean you did not want to hear the words - like "What you don't know won't hurt you./ What the eye doesn't see, the heart doesn't grieve over."
- you could mean that - especially when someone asks you something - you want to have another way of communication,
- like "beg me"
- like "I will never listen to you until I got forced"
- like "my ego forbids me to communicate about the topic with you, so find a way around"
That answer "ich hab Dich nicht gehört" has also different wordings which could fit (regarding relationship of speakers) to interpretations mentioned above:
- Wie bitte?
- Was war das?
- Ich habe Dich nicht verstanden.
- Kannst Du das nochmal sagen?
- Wie meinen?
- Ich habe Dich nicht richtig gehört.
As you might figure out, with a fitting verbal & nonverbal expression these replies could be anything like
- acustic problem
- content problem
- wording problem
- context problem
That is my observation, why people started to say
Ich habe Dich akustisch nicht verstanden.
to emphasize exactly and only this reason for a lack of a better fitting answer.