Why do we not say "Ameen" to the one who says it to us after the prayer

The questioner : Why, Shaykh, when a man says to us "May Allah accept it," do we not say "Ameen" to him?

The Shaykh : Because you know that saying "May Allah accept it" after the prayer is a religious innovation.
The student : ... after the prayer is a religious innovation.

The Shaykh : All right, now, may Allah turn to us and to you in mercy, you have put yourself in a difficult situation, now, now, if someone says to you "May Allah accept it," what do you say to him?
The student : He did not hear the question.
Another student : He wants to double up.

The Shaykh : If someone after the prayer here in the mosque, comes and says to you "May Allah accept it," what do you say to him?

The questioner : I say to him, "From us and from you."

The Shaykh : And when do you say to him "From us and from you"?

The questioner: Yes.

The Shaykh: Yes.

The questioner : This is a good question.

The Shaykh : ... .
The student : The Shaykh fell, a serious fall, when his son fell he said "Allah" and not "In the name of Allah."
Another student : Yes, look, we have many studies, Shaykh, there are ten minutes left.

The Shaykh : The help has come to you, the help has come to you.
The student : There is an important point and I would like you to record it here, in a published book.

The Shaykh : How much is the time? Listen, you have preceded him, 'Ukkashah.