Anonymous931 It is a thing in India due to several reasons, sometimes at disputes, agreements etc. and all sort of stuff, sellers sometimes say things which are not meant to be said, for example: Let’s say I am some builder/seller now I make extra deceptive claims, so that I can just get the thing/service sold immediately and get the money out of your wallet easily, now when you get to know his/her claims were false, you will have an evidence (i.e the call recording).
Scenario 1: If there is a call recording with an announcement
The seller/aggregator will simply ask you to turn off the recording and call again *Ouch
Scenario 2: Call recording without announcement
You know, now you have an evidence
Remember, this is just an example for one of the scenarios, there are many other scenarios where the call recording feature without announcement becomes a blessing in India. (I am not sure about other parts of the world)