It is, because this used to apply to most conversations. Even when overheard, they would likely be forgotten by who heard them, not have heard everything, not known who was talking, etc. If the conversation became interesting for an investigation, simply finding a witness would take significant time from limited police officers, the witness may not wish to cooperate, their memory would be imperfect, and perhaps most importantly, it would quickly become common knowledge, via gossip, what the police is snooping for.

Now most conversations have moved online, and a secret record can be cheaply created of exactly who is talking to who, when, how often, and in the absence of encryption, even what they are saying. Phones we all carry, even without spyware apps, can be located through signal triangulation, before we even get to facial recognition and omnipresent cameras, smartphone or otherwise.

That, theoretically, we can recover some of the privacy we used to have (so long as we don't get targeted surveillance, which has become so effective defeating it is nearly hopeless), does not mean that, in practice, privacy has been massively eroded for the average person.