you might be surprised how many CEOs respond and although I agree that they often have someone screening their in box that is not surprising given how busy they are and what matters is how the issue is dealt with. Of course there exist those CEOs who won't even respond to (or ensure at least someone does) complaints

When I worked on the railway I remember chatting about customer service with a train company MD and he told me that if he was in and not in meetings he would take calls from those asking to speak to the MD to complain and he said that many were so surprised to get through they forgot why they had rung!

A good CEO is someone who will deal with both the complaints and the bouquets