If the change was in language as a whole it would make some measure of sense. Languages are of course organic and new words come in but in this case it is not a natural transition but more of a deliberate supplanting of a word that is by all accounts, perfectly legit.
I grew up in a time when we called this Islamic month ‘Ramazan.’ It was not a conscious choice, just what the grandparents and elders called it and we were happy in following their legacy. We were also taught that when saying goodbye we should say ‘Khuda Hafiz’ and some families which had immigrated from Uttar Pradesh in India, including mine, were more inclined towards ‘adaab’ as a mode of greeting than salaam.
It started changing in the 80s with the PTV news anchor saying ‘Allah Hafiz’ at the end of the program. Some people did notice and talked about it but it was a military dictatorship and the man in charge was a known zealot. ‘It’s a passing trend’, was the general refrain. It was thought that things would go back once the dictatorship was over. How wrong they were.
Then I noticed more and more people who were hesitant in replying to my ‘adaab’ with the usual response, ‘jeetay raho’, literally: have a long and blessed life. These were not people who had always used the ‘salaam’, no these were folks who’s fathers, grandfathers, uncles and aunts all had lived and died using the same mode of salutations and greetings. And now they were replying back with ‘walekum adaab’, a rather cumbersome response which was neither here nor there. Then came snide comments about how ‘adaab’ is irreligious. About how it is decadent and a hangover from a previous era which should be consigned to the dustbin of history. About how it was used only to greet Hindus in India and so has no place in an (overtly) Islamic country. With time, most even called it downright blasphemous and refused to acknowledge it.