interpreter

I have a question about vrs and deaf callers. Maybe someone can give me some insight.

Why do some deaf callers tell the interpreters not to announce that this is a vrs call? I think I am a good interpreter, but it is very awkward for me to voice naturally in these calls.

Sometimes, the deaf caller does not sign clear and while I'm clarifying, I hear the hearing caller saying "hello? are you there?"

I'm not trying to control the call, nor am I putting down anyone who decides to do this, just trying to understand why they think this would make a smooth call?

Thanks.