I have come to form an incredible distaste for the arrogance and hubris of so many executives. The courtesy of a reply to an outreach, from someone you know, is just not that difficult. Just a simple acknowledgement is not that hard and really should not be too much of a demand on your “incredibly valuable” time.
*P.S. I believe mid-level managers are learning from their senior execs, emulating them, and forming the same bad habits. They especially need to remember that… Your Brand is what you do; Your Reputation is what people Remember AND Share!