Irony is defined as an event that seems deliberately contrary to what one expects and is often amusing as a result. The contrary of being responsive is to be slow or never responsive. However, to NOT hear back from someone is NOT amusing.
We live in a world where we have the world literally at our fingertips. At a time we have the ability to be responsive in a plethora of ways: text, email, call, post, so many of us are less responsive than when we had only land lines.
How can that be? How can we be worse at telecommunication than we were back in the stone ages when we had only the antiquated answering machines and human receptionists? We often are worse in the time we take to reply than when we had so fewer options.
Nike invented the JUST DO IT slogan. When it comes to response, JUST DO IT. Whether we think we are waiting for more information or whatever excuse we tell ourselves, there is no excuse.
Regardless of where you are on the organizational chart, JUST DO IT. Just answer and answer fast. It will always serve you well to be known as responsive. It will never serve you well to be tardy in your response although we can all find examples of people, even successful people, who have slow response times.