Most conversations are based on a pretext that individuals understand. In fact, if someone entering a conversation doesn't know that pretext it could awkward for them. That's why most people enter a conversation by saying something neutral like 'hello' and not by saying 'wow is the food horrible here!'. You never know who is listening. You wouldn't greet your boss the same way you greet your mother for instance (in most cases).

The tl/dr question here is 'Do you take any precondition (like relationship) into account before the parties begin chatting?'